Technical Reference Options and Adapters Volume 2 1of5

8/2/2019 Technical Reference Options and Adapters Volume 2 1of5

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TechnicalReferenceOptions and AdaptersVolume 2

Personal ComputerHardware ReferenceLibrary


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Revised Edition (April 1984)The following paragraph does not apply to the United Kingdom or any country where suchprovisions are inconsistent with local law: International Business Machines Corporat ionprovides this manual "as is," without warranty of any kind, either expressed or implied,including, but not limited to the particular purpose. IBM may make improvements and/orchanges in the product(s) and/or the program(s) described in this manual at any time.This product could include technical inaccuracies or typographical errors. Changes aremade periodically to the information herein; these changes will be incorporated in neweditions of the publication.It is possible that this material may contain reference to, or information about, IBMproducts (machines or programs), programming, or services that are not announced inyour country. Such references or information must not be construed to mean that IBMintends to announce such IBM products, programming, or services in your country.Products are not stocked at the address below. Requests for copies of this product and fortechnical information about the system should be made to your authorized IBM PersonalComputer dealer.The following paragraph applies only to the United States and Puerto Rico: A Reader'sComment Form is provided at the back of this publication. I f the form has been removed,address comments to: IBM Corp., Personal Computer, P.O. Box 1328-C, Boca Raton,Florida 33432. IBM may use or distribute any of the information you supply in any way itbelieves appropriate without incurring any obligations whatever. Copyright International Business Machines Corporation 1981, 1982, 1983, 1984ii


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Federal Communications CommissionRadio Frequency Interference StatementWarning: The equipment described herein has been certifiedto comply with the limits for a Class B computing device,pursuant to Subpart J of Part 15 of the FCC rules. Onlyperipherals (computer input/output devices, terminals,printers, etc.) certified to comply with the Class B limits maybe attached to the computer. Operation with non-certifiedperipherals is likely to result in interference to radio and TVreception. I f peripherals not offered by IBM are used with theequipment, it is suggested to use shielded grounded cableswith in-line filters if necessary.CAUTIONThe product described herein is equipped with a groundedplug for the user's safety. I t is to be used in conjunction witha properly grounded receptacle to avoid electrical shock.

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- - - -- - - -- ---- - -- ---- - - - ------_ . - Personal ComputerHardware ReferenceLibrary

mMMonochromeDisplay and PrinterAdapter

6361511


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Contents

Introduction ................................... 1Monochrome Display Adapter Function .............. 1Description ................................ 1Programming Considerations .................. 5Specifications .............................. 9Printer Adapter Function ........................ 11Description ............................... 11Programming Considerations ................. 13Specifications ............................. 17Logic Diagrams ................................ 19

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IntroductionThe IBM Monochrome Display and Printer Adapter has twofunctions. The first is to provide an interface to the IBMMonochrome Display. The second is to provide a parallelinterface for the IBM Printers. We will discuss this adapter byfunction.

Monochrome Display Adapter Function

DescriptionThe IBM Monochrome Display and Printer Adapter is designedaround the Motorola 6845 CRT Controller module. There are4K bytes of RAM on the adapter that are used for the displaybuffer. This buffer has two ports to which the system unit'smicroprocessor has direct access. No parity is provided on thedisplay buffer.Two bytes are fetched from the display buffer in 553 ns,providing a data rate of 1.8M bytes/second.The adapter supports 256 different character codes. An 8K-bytecharacter generator contains the fonts for the character codes.The characters, values, and screen characteristics are given in "OfCharacters, Keystrokes, and Colors" in your Technical Referencesystem manual.This adapter, when used with a display containing P39 phosphor,does not support a light pen.Where possible, only one low-power Schottky (LS) load ispresent on any I/O slot. Some of the address bus lines have twoLS loads. No signal has more than two LS loads.

Monochrome Adapter 1


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Characteristics of the adapter are: Supports 80-character by 25-line screen Has direct-drive output Supports 9-PEL by 14-PEL character box Supports 7-PEL by 9-PEL character Has 18-kHz monitor Has character attributes

2 Monochrome Adapter


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The following is a block diagram of the monochrome displayadapter portion of the IBM Monochrome Display and PrinterAdapter.

ProcessorAddress

ProcessorData

AOChipSelect

TimingSignals

(12) Memory( 1 ~ AddressMultiplexer

DataBusGating

BDO-7 I (8)MA

MC6845CRTC.

r

(10)

2K MemoryCharacterCode

(8)(8)

I""" CharacterClock

Octal 1Latch

f--RA Character

(4) -.. Generator

DOTCLK

Shift L... ..Register ..

Serial DotsHSYNC, VSYNC, CURSOR, DISPEN

CharacterClock

(10)

2K MemoryAttribute

,IrOctalLatch

AttributeDecode

I

VideoProcessLogic

*onitorDirect DriveOutputs

IBM Monochrome Display Adapter Block Diagram



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Programming ConsiderationsThe following table summarizes the 6845 controller module'sinternal data registers, their functions, and their parameters. Forthe IBM Monochrome Display, the values must be programmedinto the 6845 to ensure proper initialization of the display.

IBM MonochromeRegister Register Program DisplayNumber File Unit (Address in hex)

RO Horizontal Total Characters 61R1 Horizontal Displayed Characters 50R2 Horizontal Sync Position Characters 52R3 Horizontal Sync Width Characters FR4 Vertical Total Character Rows 19R5 Vertical Total Adjust Scan Line 6R6 Vertical Displayed Character Row 19R7 Vertical Sync Position Character Row 19R8 Interlace Mode --------- 02R9 Maximum Scan Line Scan Line D

AddressR10 Cursor Start Scan Line BR11 Cursor End Scan Line CR12 Start Address (H) --------- 00R13 Start Address (Ll --------- 00R14 Cursor (H) --------- 00R15 Cursor (L) --------- 00R16 Reserved --------- --R17 Reserved --------- --

To ensure proper initialization, the first command issued to theIBM Monochrome Display and Printer Adapter must be sent tothe CRT control port 1 (hex 3B8), and must be a hex 01, to setthe high-resolution mode. I f this bit is not set, the system unit'smicroprocessor's access to the adapter must never occur. I f thehigh-resolution bit is not set, the system unit's microprocessor willstop running.System configurations that have both an IBM MonochromeDisplay and Printer Adapter, and an IBM Color/GraphicsMonitor Adapter, must ensure that both adapters are properlyinitialized after a power-on reset. Damage to either display mayoccur if not properly initialized.



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The IBM Monochrome Display and Printer Adapter supports 256different character codes. In the character set are alphanumericsand block graphics. Each character in the display buffer has acorresponding character attribute. The character code must be aneven address, and the attribute code must be an odd address inthe display buffer.7 6 5 4 3 2 0

Character CodeEven Address (M)

7 6 5 4 3 2 0

FI R G I B I I G B I Attribute CodeOdd Address (M + 1)I I I I

ForegroundIntensityBackgroundBlink

The adapter decodes the character attribute byte as definedabove. The blink and intensity bits may be combined with theforeground and background bits to further enhance the characterattribute functions listed below:Background Foreground

R G B R G B Function0 0 0 0 0 0 Non-Display0 0 0 0 0 1 Underline0 0 0 1 1 1 White Character/Black Background1 1 1 0 0 0 Reverse Video

The 4K display buffer supports one screen of the 25 rows of 80characters, plus a character attribute for each display character.The starting address of the buffer is hex BOOOO. The displaybuffer can be read using direct memory access (DMA); however,at least one wait state will be inserted by the system unit'smicroprocessor. The duration of the wait state will vary, becausethe microprocessor/monitor access is synchronized with thecharacter clock on this adapter.



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Interrupt level 7 is used on the parallel interface. Interrupts canbe enabled or disabled through the printer control port. Theinterrupt is a high-level active signal.The following table breaks down the functions of the I/O addressdecode for the adapter. The i/O address decode is from hex 3BOthrough hex 3BF. The bit assignment for each I/O addressfollows:

1/0 RegisterAddress Function3BO Not Used3B1 Not Used3B2 Not Used3B3 Not Used3B4 6845 Index Register3B5 6845 Data Register3B6 Not Used3B7 Not Used3B8 CRT Control Port 13B9 Reserved3BA CRT Status Port3BB Reserved3BC Parallel Data Port3BD Printer Status Port3BE Printer Control Port3BF Not Used

1/0 Address and Bit Map



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BitNumber Function

0 + High Resolution Mode1 Not Used2 Not Used3 +Video Enable4 Not Used5 + Enable Blink6,7 Not Used

6845 CRT Control Port 1 (Hex 388)

BitNumber Function

0 + Horizontal Drive1 Reserved2 Reserved3 + Black/White Video

6845 CRT Status Port (Hex 38A)



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Specifications

At Standard TTL LevelsGroundGround

Not UsedIBM Not UsedMonochrome Not UsedDisplay + Intensity

+ Video+ Horizontal- Vertical

9-PinMonochromeDisplayconnector

o1 ~ 6 5U 9o

1234 IBMMonochrome5 Display and6 Printer Adapter789

Note: Signal voltages are 0.0 to 0.6 Vdc at down level and + 2.4 to 3.5Vdc at high level.

Connector Specifications



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Printer Adapter Function

DescriptionThe printer adapter portion of the IBM Monochrome Display andPrinter Adapter is specifically designed to attach printers with aparallel-port interface, but it can be used as a generalinput/output port for any device or application that matches itsinput/output capabilities. I t has 12 TTL-buffer output points,which are latched and can be written and read under programcontrol using the microprocessor In or Out instruction. Theadapter also has five steady-state input points that may be readusing the microprocessor's In instructions.In addition, one input can also be used to create a microprocessorinterrupt. This interrupt can be enabled and disabled underprogram control. A reset from the power-on circuit is also ORedwith a program output point, allowing a device to receive a'power-on reset' when the system unit's microprocessor is reset.The input/output signals are made available at the back of theadapter through a right-angle, printed-circuit-board-mounted,25-pin, D-shell connector. This connector protrudes through therear panel of the system unit or expansion unit, where a cable maybe attached.When this adapter is used to attach a printer, data or printercommands are loaded into an 8-bit, latched, output port, and thestrobe line is activated, writing data to the printer. The programthen may read the input ports for printer status indicating whenthe next character can be written, or it may use the interrupt lineto indicate "not busy" to the software.The output ports may also be read at the card's interface fordiagnostic loop functions. This allows faults to be isolated to theadapter or the attaching device.



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The following is a block diagram of the printer adapter portion ofthe Monochrome Display and Printer Adapter.8 25-Pin D-Shell

L ConnectorBus B U f f e ~ r 8 : : : . . . . > - l ~ D a t a Latc ..h _ . . . . . , 8 " - - ~ -.. ..Enable ClockTrans- 1 4 C 8 ~ ___+-____ceiverr IRL. . . - - - . .J

,DIRReadData

O.C.Drivers

Write DataCommand ~ : : . . : . . : . . : ~ : . . . . : . - : ____ ---.J

Reset

Decoder Write ControlRead StatusRead

I Control

BusBuffersEnable

..

Y EnablerPrinter Adapter Block Diagram


5

r.

ControlLatch

4 Clock f -

rl Clear

SLCTINSTROBE

I - - - - r ~ AUTOFDXTINIT

SLCTPEACKBUSY


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Programming ConsiderationsThe printer adapter portion of the IBM Monochrome Display andPrinter Adapter responds to five I/O instructions: two outputand three input. The output instructions transfer data into 2latches whose outputs are presented on pins of a 25-pin D-shellconnector.Two of the three input instructions allow the system unit'smicroprocessor to read back the contents of the two latches. Thethird allows the system unit's microprocessor to read the real-timestatus from a group of pins on the connector.A description of each instruction follows.

IBM Monochrome Display &Printer AdapterOutput to address hex 3BC

Bit 7 Bit 6 Bit 5 Bit4Pin 9 Pin 8 Pin 7 Pin 6

The instruction captures data from the data bus and is present onthe respective pins. Each of these pins is capable of sourcing 2.6rnA and sinking 24 rnA.It is essential that the external device does not try to pull theselines to ground.

IBM Monochrome Display &Printer AdpaterOutput to address hex 3BE

Bit4IRQEnable

This instruction causes the latch to capture the five leastsignificant bits of the data bus. The four least significant bitspresent their outputs, or inverted versions of their outputs, to the



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respective pins as shown in the previous figure. I f bit 4 is writtenas aI , the card will interrupt the system unit's microprocessor onthe condition that pin 10 changes from high to low.These pins are driven by open-collector drivers pulled to +5 Vdcthrough 4.7 kQ resistors. They can each sink approximately 7 mAand maintain 0.8 volts down-level.

IBM Monochrome Display &Printer AdapterInput from address hex 3BC

This instruction presents the system unit's microprocessor withdata present on the pins associated with the output to hex 3BC.This should normally reflect the exact value that was last writtento hex 3BC. I f an external device should be driving data on thesepins at the time of an input (in violation of usage ground rules),this data will be ORed with the latch contents.

IBM Monochrome Display &Printer AdapterInput from address hex 3BD

This instruction presents the real-time status to the system unit'smicroprocessor from the pins as follows.

Bit 7 Bit 6 Bi t 5 I Bit4 Bit 3 I Bi t 2 I Bit 1 I Bit 0 IPin 11 Pin 10 Pin 12 I Pin 13 Pin 15 I - I - r - 1

IBM Monochrome Display &Printer AdapterInput from address hex 3BE



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This instruction causes the data present on pins 1, 14, 16, 17, andthe IRQ bit to be read by the system unit's microprocessor. Inthe absence of external drive applied to these pins, data read bythe system unit's microprocessor will match data last written tohex 3BE in the same bit positions. Notice that data bits 0-2 arenot included. I f external drivers are dotted to these pins, thatdata will be ORed with data applied to the pins by the hex 3BElatch.

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0-IRQ Pin 17 Pin 16 Pin 14 Pin 1

EnablePor= 0 Por = 1 Por=O Por= 1 Por= 1

These pins assume the states shown after a reset from the systemunit's microprocessor.



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Specifications

Printer

At Standard TTL LevelsSignalName- Strobe+ D.ata Bit 0+ Data Bit 1+ Data Bit 2+ Data Bit 3+ Data Bit 4+ Data Bit 5+ Data Bit 6+ Data Bit 7- Acknowledge+ Busy+ P. End (out of paper)+ Select-Auto Feed- Error- Initialize Printer- Select InputGround

Connector Specifications

13

AdapterPin Number

123456789101112131415161718-25

0 14 250

IBMMonochrDisplay aPrinterAdapter

ornend



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2 74LSI57

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MonochromeDisplay Adapter (Sheet 3 of 10)


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PIN 11---

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- - - --------- - -- ---- - - - -- - - --_ . - Personal ComputerHardware ReferenceLibrary

mM Color/GraphicsMonitor Adapter

6361509


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i i


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Contents

Description .................................... 1Controller ................................. 5Mode Set Register . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Display Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Character Generator ......................... 5Timing Generator ........................... 6Composite Color Generator ................... 6Alphanumeric Mode ......................... 6Graphics Modes ............................ 9Basic Operations ........................... 12Programming Considerations ..................... 15Programming the Mode Control and Status Register 15Programming the 6845 CRT Controller ......... 15Color-Select Register ....................... 18Mode-Control Register ...................... 19Mode-Control Register Summary .............. 20Status Register ............................ 20Sequence of Events for Changing Modes ........ 21Memory Requirements ...................... 22Specifications ................................. 23Logic Diagrams ................................ 27

Index ........................................ Index-l

iii


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iv


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DescriptionThe IBM Color/Graphics Monitor Adapter is designed to attachto the IBM Color Display, to a variety of television-frequencymonitors, or to home television sets (user-supplied RF modulatoris required for home television sets). The adapter is capable ofoperating in black-and-white or color. I t provides three videointerfaces: a composite-video port, a direct-drive port, and aconnection interface for driving a user-supplied RF modulator. Alight pen interface is also provided.The adapter has two basic modes of operation: alphanumeric(A/N) and all-points-addressable (APA) graphics. Additionalmodes are available within the A/N or APA graphics modes. Inthe A/N mode, the display can be operated in either a 40-columnby 25-row mode for a low-resolution monitor or home television,or in an 80-column by 25-row mode for high-resolution monitors.In both modes, characters are defined in an 8-wide by 8-highcharacter box and are 7-wide by 7-high, double dotted characterswith one descender. Both uppercase and lowercase characters aresupported in all modes.The character attributes of reverse video, blinking, andhighlighting are available in the black-and-white mode. In thecolor mode, 16 foreground and 8 background colors are availablefor each character. In addition, blinking on a per-character basisis available.The monitor adapter contains 16K bytes of storage. As anexample, a 40-column by 25-row display screen uses 1000 bytesto store character information and 1000 bytes to storeattribute/color information. This means that up to eight screenscan be stored in the adapter memory. Similarly, in an 80-wide by25-row mode, four display screens can be stored in the adaptermemory. The entire 16K bytes of storage in the display adapterare directly accessible by the processor, which allows maximumprogram flexibility in managing the screen.In A/N color modes, it is also possible to select the color of thescreen's border. One of 16 colors can be selected.

Color/Graphics Monitor Adapter 1


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In the APA graphics mode, there are two resolutions available: amedium-resolution color graphics mode (320 PELs by 200 rows)and a high-resolution black-and-white graphics mode (640 PELsby 200 rows). In the medium-resolution mode, each pictureelement (PEL) may have one of four colors. The backgroundcolor (Color 0) may be any of the 16 possible colors. Theremaining three colors come from one of the twoprogram-selectable palettes. One palette containsgreen/red/brown; the other contains cyan/magenta/white.The high-resolution mode is available only in black-and-whitebecause the entire 16K bytes of storage in the adapter is used todefine the on or off state of the PELs.The adapter operates in noninterlace mode at either 7 or 14 MHz,depending on the mode of the operation selected.In the A/N mode, characters are formed from a ROS charactergenerator. The character generator contains dot patterns for 256different characters. The character set contains the followingmajor groupings of characters. 16 special characters for game support 15 characters for word-processing editing support 96 characters for the standard ASCII graphics set 48 characters for foreign-language support 48 characters for business block-graphics support (for thedrawing of charts, boxes, and tables using single and doublelines) 16 selected Greek characters 15 selected scientific-notation charactersThe color/graphics monitor function is on a single adapter. Thedirect-drive and composite-video ports are right-angle mountedconnectors on the adapter, and extend through the rear panel of

2 Color/Graphics Monitor Adapter


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the system unit. The direct-drive video port is a 9-pin, D-shell,female connector. The composite-video port is a standard femalephonojack.The display adapter uses a Motorola 6845 CRT Controller device.This adapter is highly programmable with respect to raster andcharacter parameters. Therefore, many additional modes arepossible with programming of the adapter.On the following page is a block diagram of the Color/GraphicsMonitor Adapter.



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rocessorAddress o.

..

ProcessorData ..

4

AddressLatch

Address6845 LatchCRTController

Palette/Overscan

ModelControl

,o . Display Input..

Buffer r- - Buffer(16K Bytes)

,Ir OutputLatchData Datar- Latch Latchf .. Graphics- ... Serializer

o. Character Alpha.. Generator SerializerROM

Timing.... Generator

& Control

Color/Graphics Monitor Adapter Block Diagram

....

..... n

I--

I--

rL:....

o.

o.

ProcessoData

ColorEncoder r-.

I.. ..

CompositeColor r-.Generator

RGB

HorizontalVertical


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ControllerThe controller is a Motorola 6845 Cathode Ray Tube (CRT)Controller. It provides the necessary interface to drive theraster-scan CRT.

Mode Set RegisterThe mode set register is a general-purpose, programmable, I/Oregister. It has I/O ports that may be individually programmed.Its function in this adapter is to provide mode selection and colorselection in the medium-resolution color-graphics mode.

Display BufferThe display buffer resides in the processor-address space, startingat address hex B8000. It provides 16 bytes of dynamicread/write memory. A dual-ported implementation allows theprocessor and the graphics control unit access to this buffer. Theprocessor and the control unit have equal access to this bufferduring all modes of operation, except in the high-resolutionalphanumeric mode. In this mode, only the processor should haveaccess to this buffer during the horizontal-retrace intervals.While the processor may write to the required buffer at any time,a small amount of display interference will result if this does notoccur during the horizontal-retrace intervals.

Character GeneratorA ROS character generator is used with 8K bytes of storage thatcannot be read from or written to under program control. This isa general-purpose ROS character generator with three characterfonts. Two character fonts are used on the Color/GraphicsMonitor Adapter: a 7-high by 7-wide double-dot font and a7 -high by 5-wide single-dot font. The font is selected by ajumper (P3). The single-dot font is selected by inserting thejumper; the double-dot font is selected by removing the jumper.



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Timing GeneratorThis generator produces the timing signals used by the 6845 CRTController and by the dynamic memory. It also solves theprocessor/ graphic controller contentions for access to the displaybuffer.

Composite Color GeneratorThis generator produces base-band-video color information.

Alphanumeric ModeEvery display character position in the alphanumeric mode isdefined by two bytes in the regen buffer (a part of the monitoradapter), not the system memory. Both the Color/GraphicsMonitor Adapter and the Monochrome Display and PrinterAdapter use the following 2-byte character-attribute format.

Display-Character Code Byte Attribute Byte7 6 543 2 o 7 6 543 2 o

The following table shows the functions of the attribute byte.Attribute Function Attribute Byte

7 6 5 4B R G BFG Background

Normal B 0Reverse Video B 1Nondisplay (Black) B 0Nondisplay (White) B 1I = Highlighted Foreground (Character)B= Blinking Foreground (Character)

0 01 10 01 1


3 2 1I R G

ForegroundI 1 1I 0 0I 0 0I 1 1

0B

1001


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The definitions of the attribute byte are in the following table.7 654 3 2 1 0IBIR G B I I IR G BI

I I L---I _ ~ : ~ n ~ ~ e : : i : ~ n d Color- : Background ColorBlinking

In the alphanumeric mode, the display can be operated in either alow-resolution mode or a high-resolution mode.The low-resolution alphanumeric mode has the following features: Supports home color televisions or low-resolution monitors. Displays up to 25 rows of 40 characters each. Has a ROS character generator that contains dot patterns fora maximum of 256 different characters. Requires 2,000 bytes of read/write memory (on the adapter). Has an 8-high by 8-wide character box. Has two jumper-controlled character fonts available: a 7-highby 5-wide single-dot character font with one descender, and a7-high by 7-wide double-dotted character font with one

descender. Has one character attribute for each character.The high-resolution alphanumeric mode has the followingfeatures: Supports the IBM Color Display or other color monitor withdirect-drive capability. Supports a black-and-white composite-video monitor. Displays up to 25 rows of 80 characters each.



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Has a ROS display generator that contains dot patterns for amaximum of 256 characters. Requires 4,000 bytes of read/write memory (on the adapter). Has an 8-high by 8-wide character box. Has two jumper-controlled character fonts available: a 7-highby 5-wide single-dot character font with one descender, and a7-high by 7-wide double-dot character font with onedescender. Has one character attribute for each character.The Color/Graphics Monitor Adapter will change foreground andbackground colors according to the color value selected in theattribute byte. The following figure shows the color values forthe various red, green, blue, and intensity bit settings.

R G B I Color0 0 0 0 Black0 0 1 0 Blue0 1 0 0 Green0 1 1 0 Cyan1 0 0 0 Red1 0 1 0 Magenta1 1 0 0 Brown1 1 1 0 White0 0 0 1 Gray0 0 1 1 Light Blue0 1 0 1 Light Green0 1 1 1 Light Cyan1 0 0 1 Light Red1 0 1 1 Light Magenta1 1 0 1 Yellow1 1 1 1 White (High Intensity)

Note: Not all Monitors recognize the intensity (I) bit.



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Graphics ModesThe Color/Graphics Monitor Adapter has three graphics modes:low-resolution, medium-resolution, and high-resolution colorgraphics. However, only medium- and high-resolution graphicsare supported in ROM. The following figure shows these modes.

Mode Horizontal Vertical Number of Colors Available(PELs) (Rows) (Includes Background Color)Low Resolution 160 100 16 (Includes black-and-white)Medium 320 200 4 Colors TotalResolution 1 of 1 6 fo r Background and1 of Green, Red, or Brown or

1 of Cyan, Magenta, or WhiteHigh Resolution 640 200 Black-and-white only

Low-Resolution Color/Graphics ModeThe low-resolution mode supports home televisions or colormonitors. This mode, not supported in ROM, has the followingfeatures: Contains a maxImum of 160 PELs by 100 rows, with each

PEL being 2-high by 2-wide. Specifies 1 of 16 colors for each PEL by the I, R, G, and Bbits. Requires 16,000 bytes of read/write memory on the adapter. Uses memory-mapped graphics.

Medium-Resolution Color/Graphics ModeThe medium-resolution mode supports home televisions or colormonitors. I t has the following features: Contains a maximum of 320 PELs by 200 rows, with each

PEL being I-high by I-wide.



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Preselects 1 of 4 colors for each PEL. Requires 16,000 bytes of read/write memory on the adapter. Uses memory-mapped graphics. Formats 4 PELs per byte in the following manner:

7 6 5 4 3 2 oC1 CO C1 CO C1 CO C1 CO

First Second Third FourthDisplay Display Display DisplayPEL PEL PEL PEL

Organizes graphics storage into two banks of 8,000 bytes,using the following format:MemoryAddress(in hex)B8000

B9F3FBAOOO

BBF3FBBFFF

Function

Even Scans(0,2,4, ... 198)8,000 bytesNot UsedOdd Scans(1,3,5 .. 199)8,000 BytesNot Used

Address hex B8000 contains the PEL instruction for theupper-left corner of the display area.



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Color selection is determined by the following logic:C1 co Function0011

0 Dot takes on the color of 1 of 16 preselected background colors1 Selects first color of preselected Color Set 1 or Color Set 20 Selects second color of preselected Color Set 1 or Color Set 21 Selects third color of preselected Color Set 1 or Color Set 2

C 1 and CO select 4 of 16 preselected colors. This colorselection (palette) is preloaded in an I Ia port.The two color sets are:

Color Set 1 Color Set 2Color 1 is Green Color 1 is CyanColor 2 is Red Color 2 is MagentaColor 3 is Brown Color 3 is White

The background colors are the same basic 8 colors defined forlow-resolution graphics, plus 8 alternate intensities defined bythe intensity bit, for a total of 16 colors, including black andwhite.

High-Resolution Black-and-White Graphics ModeThe high-resolution mode supports color monitors. This modehas the following features: Contains a maximum of 640 PELs by 200 rows, with each

PEL being I-high by I-wide. Supports black-and-white only. Requires 16,000 bytes of read/write memory on the adapter. Addressing and mapping procedures are the same asmedium-resolution color/graphics, but the data format isdifferent. In this mode, each bit in memory is mapped to a

PEL on the screen.



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Formats 8 PELs per byte in the following manner:

First Display PELSecond Display PELThird Display PELFourth Display PELFifth Display PELSixth Display PELSeventh Display PELEighth Display PEL

Basic Operations

I I II

In the alphanumeric mode, the adapter fetches character andattribute information from its display buffer. The starting addressof the display buffer is programmable through the CRTcontroller, but it must be an even address. The character codesand attributes are then displayed according to their relativepositions in the buffer. The following addresses will produce an"AB" in the upper-left corner of a 40 by 25 screen and an "X" inthe lower-right corner.

(Even)

MemoryAddress(in hex)B8000

Starting B8001Address

LastAddress

B8002B8003

B87CEB87CF

Display BufferCharacter Code AAttribute ACharacter Code BAttribute B

Character Code XAttribute X


(Example of a 40 by 25 Screen)AB

XVideo Screen


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The processor and the display control unit have equal access tothe display buffer during all of the operating modes, except thehigh-resolution alphanumeric mode. During this mode, theprocessor gains access to the display buffer during the verticalretrace time. I f it does not, the display will be affected withrandom patterns as the microprocessor is using the display buffer.In the alphanumeric mode, the characters are displayed from apre-stored ROM character generator that contains the dotpatterns for all of the displayable characters.In the graphics mode, the displayed dots and colors, up to 16Kbytes, are fetched from the display buffer.



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Programming Considerations

Programming the Mode Control and StatusRegisterThe following I/O devices are defined on the Color/GraphicsMonitor Adapter.

HexAddress A9 AS A7 A6 A5 A4 A3 A2 A1 AD Function of Register

308 1 1 1 1 0 1 1 0 0 0 Mode Control Register (001309 1 1 1 1 0 1 1 0 0 1 Color Select Register (00130A 1 1 1 1 0 1 1 0 1 0 Status Register (01130B 1 1 1 1 0 1 1 0 1 1 Clear Light Pen Latch30C 1 1 1 1 0 1 1 1 0 0 Preset Light Pen Latch304 1 1 1 1 0 1 0 Z Z 0 6845 Index Register305 1 1 1 1 0 1 0 Z Z 1 6845 Oata RegisterZ = don't care condition

Programming the 6845 CRT ControllerThe controller has 19 internal accessible registers, which are usedto define and control a raster-scan CRT display. One of theseregisters, the index register, is used as a pointer to the the other18 registers. It is a write-only register, which is loaded from theprocessor by executing an 'out' instruction to I/O address hex3D4. The five least-significant bits of the I/O bus are loaded intothe index register.In order to load any of the other 18 registers, the index register isfirst loaded with the necessary pointer, then the data register is

Color / Graphics Monitor Adapter 15


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loaded with the information to be placed in the selected register.The data register is loaded from the processor by executing an'out' instruction to I/O address hex 3D5.The table on the next page defines the values that must be loadedinto the 6845 CRT Controller registers to control the differentmodes of operation supported by the attachment.



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40 by 25 80 by 25Address Register Register Alpha- Alpha- GraphicRegister Number Type Units I/O numeric numeric Modes

0 RO Horizontal Character Write 38 71 38Total Only

1 R1 Horizontal Character Write 28 50 28Displayed Only2 R2 Horizontal Character Write 20 5A 20Sync Position Only

3 R3 Horizontal Character Write OA OA OASync Width Only

4 R4 Vertical Total Character Write 1F 1F 7FRow Only

5 R5 Vertical Total Scan Write 06 06 06Adjust Line Only

6 R6 Vert ical Character Write 19 19 64Displayed Row Only

7 R7 Vertical Character Write 1C 1C 70Sync Position Row Only

8 R8 Interlace Write 02 02 02Mode Only

9 R9 Maximum Scan Write 07 07 01Scan Line Line OnlyAddress

A R10 Cursor Start Scan Write 06 06 06Line Only

B R11 Cursor End Scan Write 07 07 07Line Only

C R12 Start - Write 00 00 00Address (H) Only

0 R13 Start Write 00 00 00Address (L) Only

E R14 Cursor Read/ XX XX XXAddress (H) WriteF R15 Cursor Read/ XX XX XX

Address (L) Write10 R16 Light Pen (H) - Read XX XX XX

Only11 R17 Light Pen (L) - Read XX XX XX

Only

Note: All register values are given in hexadecimal6845 Register Description



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Color-Select RegisterThe color-select register is a 6-bit output-only register. Its I/Oaddress is hex 3D9, and it can be written to using a processor'out' command. The following are the bit definitions for thisregister.Bit 0 Selects blue border color in 40 by 25 alphanumericmode.Selects blue background color (CO-Cl) in 320 by 200graphics mode.Selects blue foreground color in 640 by 200 graphicsmode.Bit 1 Selects green border color in 40 by 25 alphanumericmode.Selects green background color (CO-Cl) in 320 by 200graphics mode.Selects green foreground color in 640 by 200 graphicsmode.Bit 2 Selects red border color in 40 by 25 alphanumeric mode.

Selects red background color (CO-Cl) in 320 by 200graphics mode.Selects red foreground color in 640 by 200 graphicsmode.Bit 3 Selects intensified border color in 40 by 25alphanumeric mode.Selects intensified background color (CO-Cl) in 320 by200 graphics mode.Selects intensified foreground color in 640 by 200graphics mode.Bit 4 Selects alternate, intensified set of colors in the graphicsmode.Selects background colors in the alphanumeric mode.Bit 5 Selects active color set in 320 by 200 graphics mode.



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When bit 5 is set to 1, colors are determined as follows:C1 co Set Selected0 0 Background (Defined by bits 0-3 of port hex 3D9)0 1 Cyan1 0 Magenta1 1 White

When bit 5 is set to 0, colors are determined as follows:C1 co Set Selected0 0 Background (Defined by bits 0-3 of port hex 3D9)0 1 Green1 0 Red1 1 Brown

Bit 6 Not usedBit 7 Not used

Mode-Control RegisterThe mode-control register is a 6-bit output-only register. Its I/Oaddress is hex 3D8, and it can be written to using a processor'out' command. The following are bit definitions for this register.Bit 0 A 1 selects 80 by 25 alphanumeric mode.A 0 selects 40 by 25 alphanumeric mode.Bit 1 A 1 selects 320 by 200 graphics mode.A 0 selects alphanumeric mode.Bit 2 A 1 selects black-and-white mode.A 0 selects color mode.Bit 3 A 1 enables the video signal. The video signal isdisabled when changing modes.



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Bit 4 A 1 selects the high-resolution (640 by 200)black-and-white graphics mode. One of eight colors canbe selected on direct-drive monitors in this mode byusing register hex 3D9.Bit 5 A 1 will change the character background intensity to

the blinking attribute function for alphanumeric modes.When the high-order attribute is not selected, 16background colors or intensified colors are available.This bit is set to 1 to allow the blinking function.

Mode-Control Register SummaryBits0 1 2 3 40 0 1 1 00 0 0 1 01 0 1 1 01 0 0 1 00 1 1 1 00 1 0 1 00 1 1 1 1

z = don't care condition

51111zzz

40 x 25 Alphanumeric Black-and-White40 x 25 Alphanumeric Color80 x 25 Alphanumeric Black-and-White80 x 25 Alphanumeric Color320 x 200 Black-and-White Graphics320 x 200 Color Graphics640 x 200 Black-and-White Graphics

Enable Blink Attribute640 x 200 Black-and-WhiteEnable Video SignalSelect Black-and-White ModeSelect 320 x 200 Graphics80 x 25 Alphanumeric Select

Note: The low-resolution (160 by 100) mode requires special programming and isset up as the 40 by 25 alphanumeric mode.



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Status RegisterThe status register is a 4-bit read-only register. Its I/O address ishex 3DA, and it can be read using the processor 'in' instruction.The following are bit definitions for this register.Bit 0 A 1 indicates that a regen-buffer memory access can bemade without interfering with the display.Bit 1 A 1 indicates that a positive-going edge from the lightpen has set the light pen's trigger. This trigger is resetwhen power is turned on and may also be cleared by aprocessor 'out' command to hex address 3DB. Nospecific data setting is required; the action isaddress-activated.Bit 2 The light pen switch is reflected in this bit. The switch

is not latched or debounced. A 0 indicates that theswitch is on.Bit 3 A 1 indicates that the raster is in a vertical retrace mode.Screen-buffer updating can be performed at this time.

Sequence of Events for Changing Modes1 Determine the mode of operation.2 Reset the video-enable bit in the mode-control register.3 Program the 6845 CRT Controller to select the mode.4 Program the mode-control and color-select registersincluding re-enabling the video.



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Memory RequirementsThe memory used by this adapter is self-contained. I t consists of16K bytes of memory without parity. This memory is used asboth a display buffer for alphanumeric data and as a bit map forgraphics data. The regen buffer's address starts at hex B8000.

Read/Write MemoryAddress Space (in hex)

SystemRead/WriteMemory

Display Buffer(16K Bytes)

01000

AOOOO

B8000

BCOOO

COOOO


128K ReservedRegen Area


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SpecificationsThe following pages contain card and connector specifications forthe IBM Color/Graphics Monitor Adapter.



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isplayBM Color Dor other DirMonitor ect-Drive

At Standard TTL LevelsGroundGroundRedGreenBlueIntensityReservedHorizontal DriveVertical Drive

0 6 9Color DirectDrive 9-PinD-Shell Connector

1234 Color/Graphicsrive5 Direct-D6 Adapter789

Composite Phono JackHookup to Monitor

ideoMonitor

Composite Video Signal ofApproximately 1.5 VoltsPeak to Peak AmplitudeChassis Ground

Connector Specifications (Part 1 of 21


12

Color/GraphicsteJackomposi


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P1 (4- Pin Berg Strip)for RF Modulator

Color/GraphicsMonitor Adapter

RFModulator

+ 12 Volts(key) Not UsedComposite Video OutputLogic Ground

RF Modulator Interface

htigPen

- Light Pen Input(key) Not Used

- Light Pen SwitchChassis Ground

+ 5 Volts+ 12 Volts

Light Pen InterfaceConnector Specifications (Part 2 of 2)

1234

123456

P2 (6-Pin Berg Strip)for Light-PenConnector

Color/GraphicsMonitorAdapter

Color/GraphicsMonitorAdapter



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26 C910r/ Graphics Monitor Adapter


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Logic DiagramsThe following pages contain the logic diagrams for the IBMColor/Graphics Monitor Adapter.



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'"41 :.r"'"(4) -GM'II

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Color/Graphics Monitor Adapter (Sheet 1 of 6)

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.....

..


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II --E


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."."

(1,4,6!(1,4,&)(1.'1.6)(1,4,81(1,4.S)(1,4.61(1.6)\1111

'"

'"'"'"'"'"'"

'"'"'"'"


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0n0-..,.........

="=::r;::).0a.....0..,;>=-....n>..,

(tI) + I ~ MIIZIll-RESET

(iiI U ~ N (0) +A

(O) -RESET'(4) +IIRES15) +VSYNCDLY(8) + I O C U X ~

'"8) +.0.18(8) +Alq(0) +A17Ifll +A16(Ii) +.0.1


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(31 -Q2'(31 +cASCO

131 -


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ne..=,"-e:III

a:=....=,>=-II"C....I'D.,

'"'"

'"'"'" .,

'"OJ ItHI

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,..U''''DU 12.3,4): ~ = : :!:



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(5) (OMP WID

(5) YSYN(OUTIS) HSYNCOUTIS) lOUT(6) BOUT(5) G CUTIS) II OIlT

(2) DO(2) DI(2J DZ(2) D1(2) D'I(2) D'i(2) Dr.121 D1(3) + DATA GATE

(8) -t1EI1R(8) - lOR(8) +AEN(4) + 10 READY

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111'+100n ,RlllOn

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9-PINO-TYPECONNECTOR

" " "" " "" " "" " .." " "" "" " "" .. ".-'" ""52"'i

"'-


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Index

Aalphanumeric mode 6

Bbasic operations 12

cchange modes 21character generator 5color-select register 18composite color generator 6controller 5

Ddescription 1display buffer 5

Index-l


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Ggraphics modes 9

H

high-resolution black-and-white 11low-resolution color 9medium-resolution color 9

high-resolution black-and-white graphics mode 11

Llogic diagrams 27low-resolution color/graphics mode 9

M

medium-resolution color/graphics mode 9memory requirements 22mode set register 5mode typesalphanumeric 6graphics 9mode-control register 19mode-control register summary 20modes of operation 1

Index-2


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pprogramming considerations 15programming the mode control and status register 15programming the 6845 crt controller 15

Rregisters

color-select 18

s

mode control and status 15mode set 5mode-control 19status 21

sequence of events for changing modes 21specifications 23status register 21

Ttiming generator 6

Index-3


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