User guide

16-11
MAXQ Family User’s Guide
Table 16-2. Debug Mode Commands
OP CODE
COMMAND OPERATION
0010-0000
No Operation No Operation
0010-0001
Read Register Map
Read Data from Internal Registers. This command forces the debug engine to update the CMD3:0 bits in the
ICDC to 0001b and perform a jump to ROM code at x8010h. The ROM debug service routine will load register
data to ICDB for host capture/read, starting at the lowest register location in module 0, one byte at a time in a
successive order until all internal registers are read and output to the host.
0010-0010
Read Data Memory
Read Data from Data Memory. This command requires four follow-on transfer cycles, two for the starting
address and two for the word read count, starting with the LSB address and ending with the MSB read count.
The address is moved to the ICDA register and the word read count is moved to the ICDD register by the
debug engine. This information is directly accessible by the ROM code. At the completion of this command
period, the debug engine updates the CMD3:0 bits to 0010b and performs a jump to ROM code at x8010h.
The ROM debug service routine will load ICDB from data memory according to address and count information
provided by the host.
0010-0011
Read Program Stack
Read Data from Program Stack. This command requires four follow-on transfer cycles, two for the starting
address and two for the read count, starting with the LSB address and ending with the MSB read count. The
address is moved to the ICDA register and the read count is moved to the ICDD register by the debug engine.
This information is directly accessible by the ROM code. At the completion of this command period, the debug
engine updates the CMD3:0 bits to 0011b and performs a jump to ROM code at x8010h. The ROM Debug
service routine will pop data out from the stack according to the information received in the ICDA and ICDD
register. The stack pointer is pre-decremented for each pop operation.
0010-0100
Write Register
Write Data to a Selected Register. This command requires four follow-on transfer cycles, two for the register
address and two for the data, starting with the LSB address and ending with the MSB data. The address is
moved to the ICDA register and the data is moved to the ICDD register by the debug engine. This information
is directly accessible by the ROM code. At the completion of this command period, the debug engine updates
the CMD3:0 bits to 0100b and performs a jump to ROM code at x8010h. The ROM Debug service routine will
update the select register according to the information received in the ICDA and ICDD registers.
0010-0101
Write Data Memory
Write Data to a Selected Data Memory Location. This command requires four follow-on transfer cycles, two for
the memory address and two for the data, starting with the LSB address and ending with the MSB data. The
address is moved to the ICDA register and the data is moved to the ICDD register by the debug engine. This
information is directly accessible by the ROM code. At the completion of this command period, the debug
engine updates the CMD3:0 bits to 0101b and performs a jump to ROM code at x8010h. The ROM Debug
service routine will update the selected data memory location according to the information received in the
|ICDA and ICDD registers.
0010-0110
Trace
Trace Command. This command allows single stepping the CPU and requires no follow-on transfer cycle. The
trace operation is a ‘debug mode exit, one cycle CPU execution, debug mode entry’ sequence.
0010-0111
Return
Return Command. This command terminates the debug mode and returns the debug engine to background
mode. This allows the CPU to resume its normal operation at the point where it has been last interrupted.
0010-1000
Unlock Password
Unlock the Password Lock. This command requires 32 follow-on transfer cycles each containing a byte value
to be compared with the program memory password for the purpose of clearing the PWL bit and granting
access to protected debug and loader functions. When this command is received, the debug engine updates
the CMD3:0 bit to 1000b and performs a jump to ROM code at x8010h. Data is loaded to the ICDB register
when each byte of data is received, beginning with the LSB of the least significant word first and end with the
MSB of the most significant word.
0010-1001
Read Register
Read from a Selected Internal Register. This command requires two follow-on transfer cycles, starting with the
LSB address and ending with the MSB address. The address is moved to ICDA register by the debug engine.
This information is directly accessible by the ROM code. At the completion of this command period, the debug
engine updates the CMD3:0 bits to 1001b and performs a jump to ROM code at x8010h. The ROM Debug
service routine will always assume a 16-bit register length and return the requested data LSB first.
Maxim Integrated