DJTG: JTAG controller subsystem

This subsystem implements a JTAG controller.

The port properties on DJTG are as follows:

  • bit 0: supports SET_SPEED command

  • bit 1: supports SET_TMS_TDI_TCK command

SET_SPEED

Sets the clock frequency.

  • subsystem: 0x02 (DJTG)

  • command type: 0x03 (short)

  • command payload: 32-bit word (requested frequency in Hz)

  • response payload: 32-bit word (actual frequency in Hz)

This command returns the actual frequency used, as adjusted by the device to match hardware capabilities.

GET_SPEED

Gets the clock frequency.

  • subsystem: 0x02 (DJTG)

  • command type: 0x04 (short)

  • command payload: none

  • response payload: 32-bit word (frequency in Hz)

SET_TMS_TDI_TCK

Sets the current state of the pins.

  • subsystem: 0x02 (DJTG)

  • command type: 0x05 (short)

  • command payload: 3 bytes:

    • byte 0: TMS state

    • byte 1: TDI state

    • byte 2: TCK state

  • response payload: none

GET_TMS_TDI_TDO_TCK

Gets the current state of the pins.

  • subsystem: 0x02 (DJTG)

  • command type: 0x06 (short)

  • command payload: none

  • response payload: 4 bytes

    • byte 0: TMS state

    • byte 1: TDI state

    • byte 2: TDO state

    • byte 3: TCK state

CLOCK_TCK

Clocks TCK for the specified number of cycles, transferring no data.

  • subsystem: 0x02 (DJTG)

  • command type: 0x07 (long)

  • command payload: 6 bytes

    • byte 0: TMS state

    • byte 1: TDI state

    • byte 2-5 (32-bit word): cycle count

  • response payload: none

  • long data OUT: none

  • long data IN: none

PUT_TDI_BITS

Shifts out data sent through OUT EP3 on the TDI pin. Optionally also shifts in data from TDO to IN EP4.

  • subsystem: 0x02 (DJTG)

  • command type: 0x08 (long)

  • command payload: 6 bytes

    • byte 0:

      • 0: only shift out data on TDI

      • 1: shift out data on TDI and shift in data from TDO

    • byte 1: TMS state

    • byte 2-5 (32-bit word): bit count

  • response payload: none

  • long data OUT: data to shift out on TDI, bit_count.ceil_div(8) bytes long, packed LSB-first

  • long data IN: if shifting in enabled, data shifted in from TDO, bit_count.ceil_div(8) bytes long, packed LSB-first; otherwise, none

GET_TDO_BITS

Shifts in data from TDO to IN EP4.

  • subsystem: 0x02 (DJTG)

  • command type: 0x09 (long)

  • command payload: 6 bytes

    • byte 0: TMS state

    • byte 1: TDI state

    • byte 2-5 (32-bit word): bit count

  • response payload: none

  • long data IN: data shifted in from TDO, bit_count.ceil_div(8) bytes long, packed LSB-first

PUT_TMS_TDI_BITS

Shifts out data sent through OUT EP3 on the TMS and TDI pins. Optionally also shifts in data from TDO to IN EP4.

  • subsystem: 0x02 (DJTG)

  • command type: 0x0a (long)

  • command payload: 5 bytes

    • byte 0:

      • 0: only shift out data on TDI+TMS (OUT EP4)

      • 1: shift out data on TDI+TMS and shift in data from TDO (OUT EP4 + IN EP4)

    • byte 1-4 (32-bit word): bit count

  • response payload: none

  • long data OUT: data to shift out on TDI+TMS, bit_count.ceil_div(4) bytes long

  • long data IN: if shifting in enabled, data shifted in from TDO, bit_count.ceil_div(8) bytes long, packed LSB-first; otherwise, none

For shifting out, TDI and TMS are interleaved LSB-first as follows:

  • bit 0: TDI for cycle 0

  • bit 1: TMS for cycle 0

  • bit 2: TDI for cycle 1

  • bit 3: TMS for cycle 1

  • …

PUT_TMS_BITS

Shifts out data sent through OUT EP3 on the TMS pin. Optionally also shifts in data from TDO to IN EP4.

  • subsystem: 0x02 (DJTG)

  • command type: 0x0b (long)

  • command payload: 6 bytes

    • byte 0:

      • 0: only shift out data on TMS

      • 1: shift out data on TMS and shift in data from TDO

    • byte 1: TDI state

    • byte 2-5 (32-bit word): bit count

  • response payload: none

  • long data OUT: data to shift out on TMS, bit_count.ceil_div(8) bytes long, packed LSB-first

  • long data IN: if shifting in enabled, data shifted in from TDO, bit_count.ceil_div(8) bytes long, packed LSB-first; otherwise, none