A SWD connection must first have been
established and the device either halted in SACI during boot or reset (pin reset or
SEC_AP reset see Chapter 5). Communication from external
host to device uses these SWD registers in SEC-AP:
- DEBUGSS:TXD (data)
- DEBUGSS:TXCTL (flags)
- Bit 0 / TXD_FULL: Indicates that TXD can be read. Set by hardware when
TXD is written, cleared by hardware when TXD is read
- Bit 1 / CMD_START: Indicates that TXD contains the first word of a
command
Communication from device to host uses these registers:
- DEBUGSS:RXD (data)
- DEBUGSS:RXCTL (flags)
- Bit 0 / RXD_FULL: Set by hardware when RXD is written, cleared by
hardware when RXD is read
- Bit 1 / CMD_ABORTED: Indicates that the previous command was aborted,
meaning a new command was started before:
- All parameter words for the previous command were received,
or
- The last response word of the previous command could be written
to RXD
- Bit 2 / CMD_WORKING: Indicates that SACI is working on a command after
receiving all parameters
- Bit 3 / CMD_ERROR: Indicates any type of error (invalid SACI command ID,
prohibited operation, invalid parameters)