OMEN ALPHA
=========
OMEN Computers - - -
https://github.com/osmibity
- - - Page: 13
MON85 reserves two "restart" interrupts: RST 0 is similar to a
physical RESET, causes a cold restart of the monitor. This
instruction should be used with CAUTION during a debugging session
because any breakpoints set in the user program will be
"forgotten", and not properly removed. RST 1 is used by MON85 to
regain control at breakpoints. Opcodes of breakpointed
instructions are replaced by RST 1 whenever the user program is
executed, and are restored whenever the monitor is re-entered.
This insures that the operation of breakpoints is transparent to
you during the debugging session.
If for any reason a 'RST 1' ($CF) instruction is encountered in
the user program (and is not a breakpoint), command mode will be
entered without the '** Breakpoint' message.
All other "restart" interrupts are re-vectored to the
corresponding locations in the first page of memory occupied by
the user program (as identified by the 'U' command).
1.2 Breakpoints
MON85 allows you to set breakpoints in your program, such that
you will be given control whenever the program reaches a
breakpoint, and can examine or change things before proceeding.
MON85 also allows you to TRACE a program, so that you can see each
instruction and register contents as it executes.
MON85 is completely transparent to the program being tested
(unless timing loops are interrupted with BREAKPOINTS or TRACE).
When a breakpoint is encountered, or an instruction is traced,
MON85 uses one stack entry on the user program stack. Since this
consists of a PUSH and a POP, it should not affect any information
stacked by the user program. However, you should be aware of this,
in case you are examining the stack, or your program trys to
reclaim data already popped from the stack. (It is very poor
practice, to write programs which depend on the stack contents
below the stack pointer).
When a breakpoint is encountered, the message '** Breakpoint n'
is printed where n is the number of the breakpoint (0-7). If TRACE
is ON, no other action is taken, otherwise command mode is entered
(If the 'A' switch (see below) is ON the registers are also
displayed).
2. MON85 COMMANDS
The following commands are recognized by MON85, and may be entered
whenever MON85 is in COMMAND MODE, which is indicated by the 'C> '
prompt:
2.1 A ON|OFF
This switch turns ON or OFF the automatic register display which
occurs whenever a breakpoint is encountered or an instruction is
stepped in trace mode (see below). The default value for 'A' is
ON.
2.2 B [0-7 address]
Sets one of eight breakpoints [0-7] at the specified address. Once
