Radio Shack TRS-80 Model II Reference Manual page 55

Model II TRSDOS
Most commands will prompt you to enter additional information or
subcommands. While entering commands and subcommands, the following
keys are useful:
rm
Returns to the? prompt and cancels the command you're in.
II
Backspaces the cursor and erases previous character.
~
Cursor back without erasing.
~
Cursor forward without erasing.
IJ]
In certain subcommands, homes the cursor.
il'!]]
In certain subcommands, tabs the cursor.
Command Description
B (Breakpoint)
Press to set a breakpoint in your program. When execution reaches a
breakpoint, control returns to the debug monitor, with the program counter
pointing to the breakpoint address. To continue from that point, press
a.
The original instruction will be executed-but the breakpoint will not be
removed. It will still be there the next time that address is reached.
Note: Place breakpoints at the beginning byte of an opcode-never in the
middle of an instruction.
Press
m
to enter the Breakpoint command.
TRSDOS
prompts you to enter
the breakpoint number. Up to eight breakpoints are allowed, so type in a
number from 1 to 8. Next
TRSDOS
prompts you to enter the new address for
that breakpoint. If the breakpoint has previously been set,
TRSDOS
displays
the old breakpoint address, and the original instruction that goes in that
address.
Note: While a breakpoint is in place,
X'DT
is displayed in the memory display
for the breakpoint address.
For example:
?
Po
#=:
1 A=2800
Puts a breakpoint (#1) at address
X'2800'.
The memory display for
X'2800'
will
show a
X'DT.
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