User guide

ManualsBrandsARM ManualsComputer HardwareVERSION 1.2

121

122

123

124

125

126

127

128

129

130

; into r3 and update the pointer

MCR p14,0,r3,c1,c0 ; Write word from r3

SUBS r1,r1,#1 ; Update counter

BNE pollout ; Loop if more words to be written

MOV r0, #0x18 ; Angel_SWIreason_ReportException

LDR r1, =0x20026 ; ADP_Stopped_ApplicationExit

SWI 0x123456 ; ARM semihosting SWI

outdata

DCB "Hello there!"

END

To execute the example:

1. Assemble outchan.s:

armasm -g outchan.s

2. Link the output object:

armlink outchan.o -o outchan.axf

The link step creates the executable file outchan.axf

3. Load the image, enable comms channel viewing, and execute the image. This procedure depends on which

debugger you are using. See:

• Using armsd

• Using AXD.

Using armsd

If you are using armsd:

1. Load the image into armsd with the command:

armsd -li -adp -port s=1 outchan.axf

2. Enable communication and open the output file, then execute the program:

ccout output

3. Quit armsd when execution finishes. You should be able to view the file and see that transfer has occurred.

Using AXD

If you are using AXD:

1. Enable channel viewing. See the description of the Control system view pop-up menu in chapter 5 of the AXD

and armsd Debuggers Guide.

2. Load the image created above into AXD.

3. Use the channel viewer in AXD. See the description of the Comms Channel processor view in chapter 5 of the

AXD and armsd Debuggers Guide

4. In the AXD main screen, select Go from the Execute menu (or press F5) to execute the image.

The data sent from the target (in this example, Hello there!) should now be displayed in the Channel Viewer

window.

8.5.3 Debugger to target communication

This is the sequence of events for message transfer from the debugger running on the host to the application running

on the core:

1. The debugger polls the debug communication control register R bit. If the R bit is clear, the debug

communication read register is clear and data can be written there for the target application to read.

2. The debugger scans the data into the debug communication read register via scan chain 2. The R bit in the

debug communication control register is automatically set by this.

3. The target application polls the R bit in the debug communication control register. If it is set, there is data in the

debug communication read register that can be read by the application, using the MRC instruction to read from

coprocessor 14. The R bit is cleared as part of the read instruction.

Debug Communications Channel