DACI (UART)

This subsystem implements an UART interface. DACI stands for "asynchronous communication interface".

The port properties for DACI are as follows:

  • bit 0: port implements a DTE device
  • bit 1: port implements a DCE device
  • bit 2: port implements RTS/CTS hardware handshaking
  • bit 3: port implements XON/XOFF hardware handshaking
  • bit 4: port supports the SET_BAUD command
  • bit 5: port supports setting of number of stop bits
  • bit 6: port supports setting of number of data bits
  • bit 7: port supports "none" parity
  • bit 8: port supports "odd" parity
  • bit 9: port supports "even" parity
  • bit 10: port supports "mark" parity
  • bit 11: port supports "space" parity

PUT

Transmits bytes.

  • subsystem: 0x08 (DACI)
  • command type: 0x03 (long)
  • command payload: 4 bytes:
    • bytes 0-3: byte count to send
  • response payload: none
  • long data OUT: data to send
  • long data IN: none

GET

Receives bytes.

  • subsystem: 0x08 (DACI)
  • command type: 0x04 (long)
  • command payload: 4 bytes:
    • bytes 0-3: max byte count to receive
  • response payload: none
  • long data OUT: none
  • long data IN: received data (up to the byte count specified in the command)

This command may receive fewer bytes than asked for: the long response should be checked for the actual received byte count.

GET_MODE

Gets current UART mode.

  • subsystem: 0x08 (DACI)
  • command type: 0x05 (short)
  • command payload: none
  • response payload: 3 bytes:
    • byte 0: number of data bits (5 to 8)
    • byte 1: encoded number of stop bits:
      • 1: 1 stop bit
      • 2: 1.5 stop bits
      • 3: 2 stop bits
    • byte 2: parity mode:
      • 0: none
      • 1: odd
      • 2: even
      • 3: mark
      • 4: space

SET_MODE

Sets current UART mode.

  • subsystem: 0x08 (DACI)
  • command type: 0x06 (short)
  • command payload: 3 bytes:
    • byte 0: number of data bits (5 to 8)
    • byte 1: encoded number of stop bits:
      • 1: 1 stop bit
      • 2: 1.5 stop bits
      • 3: 2 stop bits
    • byte 2: parity mode:
      • 0: none
      • 1: odd
      • 2: even
      • 3: mark
      • 4: space
  • response payload: none

Note that not all ports support the full range of possible values. Check with GET_MODE to see what mode has been actually set.

SET_BAUD

Sets the baud rate.

  • subsystem: 0x08 (DACI)
  • command type: 0x07 (short)
  • command payload: 32-bit word (requested baud rate)
  • response payload: 32-bit word (actual baud rate)

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

TODO: driver seems to expect 8 bytes returned, but this looks like a bug

GET_BAUD

Gets the baud rate.

  • subsystem: 0x08 (DACI)
  • command type: 0x08 (short)
  • command payload: none
  • response payload: 32-bit word (baud rate)

QUERY_STATUS

Gets the current status of the port.

  • subsystem: 0x08 (DACI)
  • command type: 0x09 (short)
  • command payload: none
  • response payload: 8 bytes:
    • bytes 0-1: number of bytes currently in the transmit buffer
    • bytes 2-3: number of bytes currently in the receive buffer
    • bytes 4-7: flags:
      • bit 0: transmit buffer is halted
      • bit 1: receive buffer is in blocking mode
      • bit 2: transmit stalled due to flow control
      • bit 3: receive stalled due to flow control
      • bit 4: transmit flow control enabled
      • bit 5: receive flow control enabled

GET_BUFFER_SIZE

Gets the buffer sizes on the device.

  • subsystem: 0x08 (DACI)
  • command type: 0x0a (short)
  • command payload: none
  • response payload: 4 bytes:
    • bytes 0-1: transmit buffer size in bytes
    • bytes 2-3: receive buffer size in bytes

PURGE_BUFFER

Purges (forcefully empties, discarding contents) transmit and/or receive buffers on the device.

  • subsystem: 0x08 (DACI)
  • command type: 0x0b (short)
  • command payload: 2 bytes:
    • byte 0:
      • 0: don't purge transmit buffer
      • 1: purge transmit buffer
    • byte 1:
      • 0: don't purge receive buffer
      • 1: purge receive buffer
  • response payload: none

HALT_TX

Halts or unhalts the transmit buffer. While the transmit buffer is halted, no bytes will be sent over the line, and PUT commands that would normally block waiting for buffer space will return an error instead.

  • subsystem: 0x08 (DACI)
  • command type: 0x0c (short)
  • command payload: 1 byte:
    • 0: unhalt transmit buffer
    • 1: halt transmit buffer
  • response payload: none

SET_RX_BLOCK

Sets the receive buffer to blocking or non-blocking mode. When in non-blocking mode, GET command will always return immediately, returning whatever is available in the buffer. When in blocking mode, it will wait for the full number of requested bytes to be available.

  • subsystem: 0x08 (DACI)
  • command type: 0x0d (short)
  • command payload: 1 byte:
    • 0: set non-blocking mode
    • 1: set blocking mode
  • response payload: none

SET_RTS_CTS_ENABLE

Enables or disables hardware RTS/CTS control flow.

  • subsystem: 0x08 (DACI)
  • command type: 0x0e (short)
  • command payload: 1 byte:
    • 0: disable RTS/CTS control flow
    • 1: enable RTS/CTS control flow
  • response payload: none

SET_XON_XOFF_ENABLE

Enables or disables hardware XON/XOFF control flow.

  • subsystem: 0x08 (DACI)
  • command type: 0x0f (short)
  • command payload: 1 byte:
    • 0: disable XON/XOFF control flow
    • 1: enable XON/XOFF control flow
  • response payload: none