A bug in the STS?
In preparation ZXA library to
publication I have encountered a strange
STS behavior when debugging examples of work
with the library. I can not say for sure:
Is this a bug or just a feature of the STS
work, but everyone should know about it so
not to seek non-existent bugs in its
code.
Thus, debugging the following piece of code:
CALL ZXA_DRAW_FRAME
INT_COUNTER EQU $ +1
LD A, 00
A interrupt hung the following snippet:
LD HL, INT_COUNTER
INC (HL)
And (an important point!) Time
ZXA_DRAW_FRAME procedure was slightly
more interruptions, ie, during her work
interruption occurred necessarily.
So, if the line CALL ZXA_DRAW_FRAME
is present (it is installed PC) and
if you go into this line of STS SS + T, then
The SP register CHANGE YOUR VALUE! And
its value must be equal to # FBxx
where xx - any number.
What it is: a bug or not? I do not know ... Know
Only, he spent several hours at
search for bugs in your code (since code
worked, if it is run, and did not work
when debugging in STS).
Here is an example program for debugging
which can interfere with expression of
this error:
DI
LD HL, # 6000
LD DE, # 6001
LD BC, # 100
LD (HL), # 61
LDIR
LD A, # C3
LD (# 6161), A
LD HL, IM2
LD (# 6162), HL
LD A, # 60
LD I, A
IM 2
EI
LOOP HALT
CALL PROC; ***
INT_CNT LD A, 00
LD BC, # 7FFE
IN A, (C)
AND 1
JR NZ, LOOP
IM 1
RET
; HL = 4000 to the time of the procedure was
; Equals approximately 1.5 interrupt
; Pentagon'e without turbo mode.
PROC LD HL, 4000
L1 DEC HL
LD A, H
OR L
JR NZ, L1
RET
IM2 PUSH HL
LD HL, INT_CNT +1
INC (HL)
POP HL
EI
RET
Type in this program, compile,
Sign in STS, protrassiruyte to line
marked'***' and her then SS + T.
Then look at the register SP - I
its value after all these actions
becomes # FB00.
But if after the line CALL PROC
add a few NOP'ov (enough to
JP x command does not cover the variable
INT_CNT), then everything will work fine.
So, in all likelihood, this problem
arises from the fact that the STS when you
SS + T just after the team puts the point
Stop and start it.
Yes, forgot to say that this was checked
in the STS v4.3, possibly in other versions of all
normal.
