[MZ-80s/700] Use of dual-port RAM

Post Reply
Posts: 135
Joined: Thu Jan 25, 2018 9:31 pm

[MZ-80s/700] Use of dual-port RAM

Post by hlide » Fri Mar 02, 2018 12:35 pm

I found an interesting link.

I was interested in Vectrex32 and I had a talk with the author which explains to me how its card dialogs with the 6809. He uses a 2KB dual-port RAM to run 6809 code dynamically. Vectrex32 has a 32-bit CPU which can be programmed in BASIC and generates 6809 code as a coprocessor to handle video and sound stuff.

I can see several possible uses for them:

1) Full reprogrammable CGROM -> CGRAM. CPU can reprogram the full 256/512 characters through a dual-port RAM. Video generator read from it and CPU can write in it. Like PGC-1200, we could also have a two-buffer to allow a switch between video frames and have some dynamic sprites generations (CPU rewriting characters in one buffer while the video generator reading from the other, allowing smooth pixel-wise animation).

2) Making the ROMs shareable between the CPU and an external device.

3) Making all the RAMs shareable between the CPU and an external device.

Post Reply