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MEMORY EXAMINE AND CHANGE M (addr)
The Memory Examine and Change function can be used to enter machine code programs
and to display and/or change the contents of memory. The Memory Examine and Change
function should be used as follows:
1.) Type M. The computer should echo the M and output a space.
2.) Type in the four digit hexadecimal address that you wish to examine and/or change.
The computer should respond with a carriage return, line feed, $, the address and the
data that is stored at this address.
3.) At this point the user has the option of advancing, either forward or backward, to the
next memory location, or changing the data stored at the displayed address and
advancing to the next location or of exiting the M function.
a.) To display the next sequential address and data, a line feed or any character other
than 0123456789ABCDEF:;^=>? or a space or a carriage return may be entered.
Any leading spaces that are entered will be ignored by the memory change
function.
b.) To display the next sequential address going backward from the present location, a
^ should be entered.
c.) To change the data stored at the displayed location, enter the new data, either with
or without a leading space. If a non-hex value, such as a 3Q is entered the data will
remain unchanged and the memory change function will be exited. If the data is
unable to be changed (write protected memory, etc.) a ? will be output and the
memory change function will be exited.
d.) To exit the Memory Examine and Change function, type a carriage return.
Below is an example. The underlined parts are what was entered by the user.
$M 0100 MEMORY LOCATION 0100 OPENED
$0100 00 . DISPLAY NEXT LOCATION
$0101 BD . DISPLAY NEXT LOCATION – SPACE IGNORED
$0102 5D . DISPLAY NEXT LOCATION
$0103 C1 01 CHANGE CONTENTS TO 01
$0104 C9 23 CHANGE CONTENTS TO 23. SPACES IGNORED
$0105 15 ^ READ PREVIOUS LOCATION
$0104 23 . DISPLAY NEXT LOCATION
$0105 15 3Q ENTER NON-HEX VALUE
$M 0105 SWTBUG CONTROL RESUMED. OPEN NEW LOCATION
$0105 15 EXIT BY HITTING CARRIAGE RETURN
$M E000 OPEN ANOTHER LOCATION
$E000 FE 56? ATTEMPTED TO CHANGE A WRITE PROTECTED MEMORY
$ SWTBUG CONTROL RESUMED
REGISTER DUMP FUNCTION R
The R command will display the current contents of the MPU's pushdown stack. “Current”
means the status of data stored on the stack immediately before SWTBUG® control is resumed.
The following is a typical register dump:
$R
$FF 16 23 17EC 0103 A042
$
CONDITION
CODES
ACC
B
ACC
A
INDEX
REG
PGM.
CTR.
STACK
PTR