UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
16 of 1269
NXP Semiconductors
UM10503
Chapter 2: LPC43xx ARM Cortex-M0 co-processor and Inter- Process
2.5.3 Example
Assume a certain task with ID 0x1234 should be executed by the ARM Cortex-M0. For
example, read data from a register level interface controlled by the ARM Cortex-M0. Text
in bold indicates a register.
The registers can either be located in the ARM Cortex-M0 SRAM, for more deterministic
access times, or in shared SRAM. If the ARM Cortex-M0 SRAM is used, then the register
data needs to be copied at initialization time. This copying takes time. The ARM
Cortex-M4 can poll a status register to determine when the transfer has finished.
The ARM Cortex-M4 initializes the command and message queues by loading the start-
and end addresses and write and read pointers.
Then the ARM Cortex-M4 loads the register values in a reserved area in common SRAM
memory. An alternative approach is that the ARM Cortex-M4 writes register per register,
however this requires more communication overhead than loading all data in one go.
Once all data has been set up, the ARM Cortex-M0 task can be started.
Table 7.
Message list
Message
Bit mask
Description
MSG_SRV_ID
0xTTTT.SS00
ARM Cortex-M0 request servicing for the task
with ID = 0xTTTT. The service type is coded in
bytes SS. The meaning of SS is proprietary per
task. SS=0x00 means the task has finished.
MSG_RD_ID
0xTTTT.PPP1, VALUE
ARM Cortex-M0 responds with VALUE to a read
of WORD with argument ID=0xPPP* from the
task with ID = 0xTTTT.
MSG_RD_STS_ID 0xTTTT.PPPR
ARM Cortex-M0 response to a read of WORD
with argument ID=0xPPP* from the task with ID
= 0xTTTT fails. Cause of the failure is coded in
R; R = 2...4
2 = invalid argument
3 = reserved
4 = reserved
MSG_WR_STS_ID 0xTTTT.PPPW
ARM Cortex-M0 response to a write with
argument ID=0xPPP* from the task with ID =
0xTTTT. Response is coded in W; W = 5...7
5 = write was successful
6 = write failed
7 = reserved
Table 8.
Command responses
Command
Possible responses
Description
CMD_RD_ID
MSG_RD_ID, VALUE
read acknowledged
MSG_RD_STS_ID
read failed
CMD_WR, WORD
MSG_WR_STS_ID
write is acknowledged as a success or failure