Motorola USB08 Betriebsanleitung PDF herunterladen (Seite 61)

8.26 Step Over O

Format:

O[Repeats] [StartAddress|*]

Command to step over a program in MCU controlled memory, that is to jump over subroutine calls.

If the next instruction is not a subroutine call, then this command behaves exactly like the Trace

command. The 'T' and 'O' commands may be freely inter-mixed. If no explicit start address is specified,

then stepping/tracing will begin at the current value of the 'T/G' address. When the 'O' command is

given, Xplor8 carries out exactly the same five operations listed under the 'T' command, with the

exception that the 'following instruction' mentioned in operation no.2 will be adjusted in the case of

subroutine calls to be the next sequential instruction rather than the instruction at the entry to the

subroutine.

'Repeats' is an optional number which specifies how many times the command is to be repeated. Note

that repeats is specified as a decimal number, unlike all other values which are entered in hexadecimal.

The value of 'Repeats' follows the letter O without a gap.

The T/G address (see Information Sidebar on page 21) is also updated to show where the last trace

instruction has stopped; so issuing the 'O' command alone will continue stepping from where the

previous trace or step operation halted.

Suppo sing that the following fragments of code are in memory:

E00E LDA ,X

E00F INC $01,SP

E012 DLYLOOP BSR DELAY

E014 FINISH PULA

E015 SWI

E016 NOP

E017 DELAY LDA #$02

E019 DLY1 DECA

E01A BNE DLY1

E01C RTS

Issuing the command:

T E00E

will begin tracing with the instruction at address $E00E, and will halt at $E00F. Issuing either 'T' or

'O' by itself will then advance tracing by one instruction, halting at $E012. Issuing 'T' alone would then

trace into the subroutine, and halt at $F017, whereas issuing the 'O' command would step over the

subroutine (the subroutine is still executed), halting at $E014.

Note also the caveat in the [~JUMP Trace] command concerning beginning tracing or stepping at an

RTS or RTI instruction.

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Motorola USB08 Betriebsanleitung Seite 61