6
FUNCTIONS
58
EPSON
S1C33 FAMILY C33 PE CORE MANUAL
6
.
5
Debug Circuit
The C
33
PE Core has a debug circuit to assist in software development by the user.
The debug circuit provides the following functions:
•
Instruction break
A debug exception is generated before the set instruction address is executed. An instruction break can be set at
three addresses.
•
Data break
A debug exception is generated when the set address is accessed for read or write. A data break can be set at
only one address.
•
Single step
A debug exception is generated every instruction executed.
•
Forcible break
A debug exception is generated by an external input signal.
•
Software break
A debug exception is generated when the
brk
instruction is executed.
•
PC trace
The status of instruction execution by the processor is traced.
When a debug exception occurs, the processor performs the following processing:
(
1
) Suspends the instruction currently being executed.
A debug exception is generated at the end of the E stage of the currently executed instruction, and is accepted at
the next rise of the system clock.
(
2
) Saves the contents of the PC and R
0
, in that order, to the addresses specified below.
PC
→
0
x
00060008
R
0
→
0
x
0006000
C
(
3
) Loads the debug exception vector located at the address
0
x
00060000
to PC and branches to the debug exception
handler routine.
In the exception handler routine, the
retd
instruction should be executed at the end of processing to return to the
suspended instruction. When returning from the exception by the
retd
instruction, the processor restores the saved
data in order of the R
0
and the PC.
Neither hardware interrupts nor NMI interrupts are accepted during a debug exception.