another day, another success 8)
yesterday i successfully tested the SHOW command for the 8-bit project, which shows the contents of memory, and takes the form
where as usual square brackets indicate that the address parameter is optional, and (if present) the address must be 4 hex characters long. if the address parameter is omitted, then output begins from the byte after the last byte show by the last SHOW command.
format of the output is
xxxx:yy yy yy yy yy yy yy yy
where ‘xxxx’ is the address of the first byte. up to 8 bytes are shown; the loop exits when the address of the next byte to be shown is an exact multiple of 8. this makes understanding the data a little easier, since each (sans argument) SHOW after the first will always show 8 bytes and start at either xxx0 or xxx8. you might recognize that this is very similar to how the apple monitor works when displaying data, and that was in fact my model.
there is one more functionality to be written and tested for SHOW, and that is the ability for the system to remember the last command entered, and then if the user hits ‘enter’ on an empty line and the last command was SHOW, to respond as if the user had entered SHOW without an argument. this will better match the apple case, where continually hitting ‘enter’ will display the next 8 bytes, allowing the user to display regions of memory 8 bytes at a time without having to type SHOW each time.
i’m not sure where i’ll go next…i need to start designing and building the real hardware at some point, and i’m just about at the point where i have the software ready for that. on the other hand, the serial port code currently uses the super serial card, which obviously won’t be available in my design (although i will be using a 6551 chip pulled from an SSC). so it would be good to get that set up on the breadboard, update the code, and test it before moving to final hardware.