Normal text - click to edit Configuring of Xilinx Virtex-II

Kjetil Ullaland, Ketil Røed, Bjørn Pommeresche, Johan Alme

TPC Electronics meeting. CERN 13-14. Jan 2005

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Overview

• Xilinx Virtex-II configuration facts

• Work so far

• Results

• Status

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Configuring Xilinx Virtex-II

• 5 built-in modes– JTAG– Master/Slave Serial– Master/Slave SelectMap

• JTAG and Slave SelectMap is chosen for RCU.

• 3 mode pins (M2, M1, M0) are used for setting the mode.

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Configuring - details

• A Xilinx Virtex is divided into Columns, which again is divided into frames.

• The XC2VP4 has:– One center column (8 frames/column)– 752 CLB Colums (48 frames/column)– 4 BRAM Columns (27 frames/column)

• DCM is included here– 2 IOB Columns (54 frames/column

• The Column number from the start is called Major Number, and the frame number in the columns is called Minor number.

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Configuring - details

• Counting of the major number is 0 in the center, the even numbers to the left, and the odd to the right.

• The Major and Minor numbers are used to locate a specific frame in the Virtex-II.

• Writing these numbers to the FAR (Frame address register) in the FPGA, makes it possible to read or write from/to this frame.

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JTAG

• JTAG is the default mode.– JTAG always work whenever connected, no matter

what mode is selected.

• Benefits: – Well known interface that is easy to use and is

supported by all companies.– Possibility to do a readback– No extra firmware/software required except what is

delivered by Xilinx.

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Slave SelectMap

• Mode pins should be set to 110 (M2, M1, M0)– Note: If connected to a 3.3V network, these inputs must

have a 100 serial resistor attached

• External clock is used for configuring.• 8 bit wide databus• 6 control/status lines • Benefits:

– Parallel data transport => fast interface.– Possibility to do readback of configuration memory.

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Slave SelectMap

cclk

Init_b

Cs_b

Rdwd_b

Prog_b

Data

busy

done

>300ns

b0 b1 b2 b3 b4 b5 b6 b7 bN

Cclk <50MHz, busy never asserted during config

* >8 cclks for startup sequence

*

Waveform showing Slave SelectMap with Controlled Clocks. Data is clocked in at each rising edge of cclk. • Note: Prog_b should only be pulled low if clearing configuration memory.

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Why use controlled clock

• Second option is to use a free running clock and toggle chip select when data is ready from the sender.

• This means danger for skew between clock and chip select signal, which may lead to the wrong data is transported.

• Controlled clock ensures that no skew or glitches will occur, as the clock is toggled when data is put on the bus.

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What is Scrubbing?

• Scrubbing is when the FPGA has been reconfigured without first deleting existing configuration.

• This is possible because there is a shadow register column for the configuration register columns.

• A scrubbing cycle should always be preceded and followed by an abort-command, according to documentation.

1.

2.

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Scrubbing

• When doing a scrubbing cycle, it’s important to stop on the column before the BRAM content.– If deleting the BRAM contant, all values stored in RAM blocks are

deleted. – Before this column, an abort is issued.

• In the beginning of the configuration file, Frame 0 in Column 0 is written to the FAR register setting the starting point of the configuration.

• If we want to do a partial reconfiguration, a different start address should be written to the FAR

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Abort command• Part of scrubbing procedure• The abort command is issued by toggling RDWR_B while cs_b is asserted.• An abort command lasts for at least four clock cycles.• A 32-bit abort status word is driven onto the databus during this time.• The abort ends when cs_b is deasserted.

Configuration abort sequence Readback abort sequence

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Abort status word

• Typical result according to documentation is:– 11011111 (no error, sync word received, no readback, no abort)– 11001111 (no error, sync word received, no readback, abort)– 10001111 (no error, no sync word, no readback, abort)– 10011111 (no error, no sync word, no readback, no abort)

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Preparing a project in ISE

• To be able to do readback or scrubbing, the selectMap bus I/O pins must stay in configuration mode after initial configuration.

• Default setting is to go back to normal user I/Os

• Binary configuration file should also be created.

• Startup clock must be set to CCLK (for selectMap).

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Files to use for configuring• <design>.bit

– A binary configuration file with header information. The configuration stream start with 0xFFFFFFFF and a synch word.

– If the bit file is used a search algorithm for the start of configuration stream must be added in software/firmware

• <design>.bin– Same as .bit-file, but without header information

• <design>.rbb– Used for readback verification. – Readback verification is a process of making a bit per bit comparison of the readback

data frames to the bitmap in the <design>.rbb readback file.• <design>.msk

– Used for readback verification.– Masks out irrelevant data, as not all readback data should be used for verification.

• All files have approximately the same size, 368KB for the Xilinx Virtex-II XC2VP4

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More information

http://www.xilinx.com• Ug012.pdf

– Virtex-II Pro and Virtex-II Pro FPGA User Guide• Ds083.pdf

– Virtex-II Pro and Virtex-II Pro X Platform FPGAs: Complete Data Sheet

• Xapp216.pdf– Correcting Single-Event Upsets Through Virtex Partial

Configuration• Xapp138.pdf

– Virtex FPGA Series Configuration and Readback

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Picture of setup

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The test design - configuring

• Changed the DCS messagebuffer-design so that Linux (ARM processor) have complete control of the RCU bus lines (data, address & ctrl)

• Wrote a device driver in C that configures the design using controlled clock scheme. (Virtexdriver.c)

• Made a simple design in the Altera CPLD that maps the selectMap bus to the RCU bus.

• This means we have a ”tunnel” going from linux directly to the SelectMap bus.

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Sketch of test designDCS board v1.52

RCU testboard

Altera Max-IICPLD

Xilinx Virtex-II

Altera FPGA withARM

LinuxFlash

(bin-file is stored)

RCU bus lines

SelectMapBus

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Configuring

• This made us able to use the cat-command in linux as:– cat virtexdesign.bin > /dev/virtex

• The device driver then controls and responds to the control signals on the selectMap bus.

• Wrote error and info messages to kernel log.

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Testdesigns for Virtex-II• Two very simple test-designs were made.

• Led 01 and Led 02 were physically in the same column in the Virtex FPGA.

Design 01

Led 01

Led 02

Led 01

Led 02

Led 03Clock Led 03Clock

Design 02

VCC

GND

GND

VCC

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Configuring with erasing configuration memory

• Controlled from software• One of the two designs sent to the device

driver using the cat command.• Without optimization the configuration time

is approx. 600ms.• Time consuming:

– Initialising Deivce driver– Writing to Kernel log– Buffering input file

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Configuring with erasing configuration memory

CCLK

CS_B

Configuration time approx 625ms

Beginning of config cycle Complete configuration

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Scrubbing• Scrubbing is tested by altering between the two

different led designs, and slightly changing the virtex_driver.c code– Cat design01.bin >/dev/virtex– Cat design02.bin >/dev/virtex– Cat design01.bin >/dev/virtex

• When doing this we could see leds switching in the middle of the configuration-cycle.

• Because led1 and led2 are in the same physical row in the virtex, they switch at the same time.

• At led3, which is driven by the same clock in both designs, there was no visible delay in the pulse. Le

d1

Led2

Led3

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Scrubbing

Led1

Led2

Led3

Led1

Led2

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Results - Configuration• Clearing Configuration Memory and configuring

successful• Scrubbing successful.

– When doing a hard scrub cycle (deleting BRAM content), the abort word is not needed, as we are writing the complete config file.

– When not deleting BRAM memory, the DCM cannot be refreshed as this in the same column as the BRAM.

• Read back status word issued when doing an Abort sequence.– Depending on when the abort was issued, different words are

issued.– Fits with documentation.

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Results – Flash memory

• Writing to Flash memory has been tested on DCS board.

• Used XJTAG to write to the Flash.– XJTAG makes it possible to clock data to the correct

pins on the FPGA and then shift it over to the Flash memory as an ordinary bus transaction.

• We can use the JTAG chain to program the Flash by manually control the IO pins on the CPLD.

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Ongoing work

• Readback and verification of configuration memory. – A prototype is being designed in C, and then

implemented in Firmware.

• Making the firmware for the CPLD on the RCU according to presented specification.