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A previously set breakpoint will remain and may be changed or removed as described
earlier. If, when using the B command, a non-hex value is entered the previous breakpoint will be
removed and SWTBUG® control will resume.
There are several things that one must be aware of when using breakpoints to insure proper
operation.
1.) The breakpoint function uses the same locations as do vectored software interrupts;
therefore, vectored software interrupts should not be used with break points.
2.) The SWI jump location, A012, will be set to E124 when breakpoints are not in use, as
after power up, and will be set to E123 when breakpoints are in use. This location
serves as a pointer to tell the computer what to do when a 3F is seen. The RESET
button will not reset this location to the non-breakpoint state. The breakpoint-activated
state can only be exited by typing B followed by a carriage return. If you are using
breakpoints in a program that “bombs out” and you hit the RESET switch, you must
clear the present breakpoint before going on to another program. If this is not done
before a new program is loaded in, the first time the B command is used one byte of the
new program will be replaced by the stored byte from the last program.
3.) Do not set a breakpoint to an address where a breakpoint is already set. Doing so will
cause the computer to lose the original program data.
DO NOT THIS IS OK
B 1377 B 1377
G B 0100
B 1377 B1377
B carriage return
4.) The breakpoint routine uses SWTBUG® RAM locations A014-A016; therefore,
programs which use these three bytes should not be used in conjunction with
breakpoints.
DISK BOOT D
SWTBUG® contains the boot necessary to initialize a SWTPC MF-68 disk system. Typing D
will transfer control to the disk operating system, (if attached). If D is accidentally typed with no
disk attached, the RESET button must be pressed. Since the disk boot contains no error
detection, it may need to be typed more than once to do a boot.
JUMP TO PROM PROGRAM Z
Typing Z will transfer control to a program stored in PROM (if applicable) whose starting
address is at C000. Typing Z is equivalent of typing J C000
BYTE SEARCH F (high address) (low address) (byte)
The F (find] command will search memory from the specified low address to tile high
address, inclusive, and will display all memory locations containing the byte specified. For
example, to find all memory locations between 0100 and 0200 that contain 8E, the following
command should be used: F 020001008E. Note that no spaces may be used between addresses
and that the high address goes first.
$F 020001008E
If a non hex value is entered, SWTBUG® control will resume.