S.Elliott's blog

MON0 routine and args.png

When calling a machine code subroutine from the Monitor, one or two additional arguments can be passed by taking advantage of the way the Monitor uses delimiters to parse arguments from its command-line and stores them in the zero-page pointers A1, A2, A3, A4...in an arbitrarily-strange order:

• The default argument is always the subroutine address, stored in A1.
• Appending a '.' delimiter allows another argument to be stored in A2.
• Inserting a '<' delimiter allows an argument to be stored in A4.

capture217.png

Back in 1983, how many users found the secret message in this instructional software?

]BRUN BARGLE

Bargle program by Sue Espinosa

Bargle Bargle Bargle

]

Clock stretching.png

Synopsis:

• Define a short datagram to be transmitted via vapor from visible screen memory.
• Encode single-cycle accurate video phase via vapor datagram.
• Construct a routine to receive the vapor datagram and synchronize itself to the video scanner.
• Write a simple BASIC program to demonstrate all that!