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commandstructure.md

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Command structure

Config Frames

0x3B looks like the “load config” command (similar to LSC_PROG_INCR_RTI for ECP5) 0x80 CRC enable 0x02 number of frames MSB 0xC8 number of frames LSB

Followed by configuration frames (including EBR) (0x2C8=712) of them in this case, gw1nr9)

Each frame seems to be: 1. Frame data, with 1s appended at the start to make it an multiple of 8 bits (guess, similar to ECP5) 2. CRC-16 that matches “CRC-16/ARC” algorithm at https://crccalc.com/ but endian swapped (optional) 3. 6x 0xFF bytes

At end of bitstream 18 more 0xFF bytes followed by 2 bytes 0x34 0x73 which are the CRC as above of the last 24 0xFF bytes

First CRC is special, like ECP5, as it also covers the commands after the preamble except the flash address.

Preamble

20 0xFF bytes, followed by two bytes “file checksum” (for early Vendor tool release), followed by 0xFF 0xFF 0xA5 0xC3 For comparison ECP5 preamble is 0xFF 0xFF 0xBD 0xB3 “File checksum” matches value displayed in programmer, unlikely actually used by hardware

Other commands

Command always followed by 3 “option” bytes, usually 0x00 except for “load config”, like ECP5 commands

0x06 (or 0x86 when bit_crc_check not set) IDCODE check (similar to ECP5 VERIFY_ID) Followed by 3x 0x00 bytes

Then the JTAG IDCODE For GW1N-1: IDCODE 0x0900281B; bytes here 0x09 0x00 0x28 0x1B For GW1NR-9: IDCODE 0x1100581B; bytes here 0x11 0x00 0x58 0x1B For GW2AR-18: IDCODE 0x0000081B; bytes here 0x00 0x00 0x08 0x1B

0x10 (or 0x90 when bit_crc_check not set)

  • [56:24]: unknown 0x00000000 (seems to be same for all devices and configs)
  • [23:16]: value depending on loading_rate (value to determine) (or 0x00 when N/A)
  • [15:14]: unknown 0x0
  • [13] : 1 when bit_compress set
  • [12] : 1 when program_done_bypass set
  • [11:0] : unknown 0x000

0x51 (or 0xD1 when bit_crc_check not set) Compress configuration

  • [56:24] : unknown 0x00FFFFFF (seems to be same for all devices and configs)
  • [23:16] : OxFF for uncompressed bitstream or a value used to replace 8x 0x00 in compress mode
  • [15:8] : OxFF for uncompressed bitstream or a value used to replace 4x 0x00 in compress mode
  • [7:0] : OxFF for uncompressed bitstream or a value used to replace 2x 0x00 in compress mode

0x0B (or 0x8B when bit_crc_check not set) only present when bit_security is set Followed by 3x 0x00 bytes

0xD2 Set SPI flash address (8 bytes)

  • [56:32]: unknown, always 0x00FFFF
  • [31:0] : SPI flash address (or 0x00000000 if N/A)

0x12 (or 0x92 when bit_crc_check not set) Unknown 0x000000

Last command before 0x3B (or 0xBB when bit_crc_check not set) config frame load command, probably equiv to LSC_INIT_ADDRESS

  • [23] : 1 when bit_crc_check set
  • [22:16]: unknown, always 0x00
  • [15:0] : number of lines in configuration data section

0x0A set USERCODE (similar to ISC_PROGRAM_USERCODE) Followed by 3x 0x00 bytes Then the 4-byte USERCODE

0x08 final command in bitstream, probably equivalent to ECP5 ISC_PROGRAM_DONE Followed by 3x 0x00 bytes

0xFF NOP/padding