Tandy 1000 MS-DOS Reference Manual page 296

Chapter 13/ The DEBUG Utility
• address2 is used to set breakpoints. These allow you to exam-
ine the register contents and flag settings in effect when a
specified address is reached during program execution.
After execution halts at a breakpoint, you can enter the Go
command again. The program resumes execution at the
instruction after the breakpoint.
• An interrupt code (OCCH) is placed at the specified break-
point addressees). When an instruction with the breakpoint
code is reached, DEBUG restores all breakpoint addresses to
their original instructions. If no breakpoint is reached, the
original instructions are not restored.
• A maximum of ten addresses can be set, in any order. If you
enter only an offset for a breakpoint address, the segment
indicated by register CS is used. Breakpoints can be set only
at addresses that contain the first byte of an 8088 opcode.
Execution stops when any breakpoint is reached.
• The user stack pointer must be valid and have 6 bytes avail-
able for the Go command. This command uses an IRET
instruction to cause a jump to the program under test. The
user stack pointer is set and the user flags, CS register, and
Instruction Pointer are pushed on the user stack.
Example
G CS : 7 5 5 il
I
ENTER
I
causes the program currently in memory to execute up to
address 7550 in the CS segment. DEBUG restores the original
instructions, displays the register contents and the flags, and the
Go command ends.
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