??? 03/06/04 18:31 Read: times |
#66126 - RE: Using an 8051 to drive a CGA card Responding to: ???'s previous message |
I originally started this thread and I have since actually built this project. It was quite fun and has been performing very well. I did this as a hobby project using parts that I already had on hand. This means using an 8751H (I have quite a few of those), an 8155 expansion chip and an original IBM CGA card. The two main reasons for using the CGA card was that it has a composite video output, and I have the IBM XT technical reference manual, which lists all the control registers and mode settings. The 8155 has a total of 22 regular i/o lines, which is exactly what I needed to address the memory and i/o ports of the CGA card and drive the data lines. Ports B and C drive address lines A0 to A13. Port A sends and receives data. The higher address bits simply needed to be fixed to produce the highest memory address range that the card is expection, so A18 was tied to ground and the others (A14 to A17 and A19) were tied to +5v. One of the 8751 ports drives the various i/o and mem r/w lines.
Using the 4k of eprom in the 8751, I was able to implement a large size character set stored in a serial eeprom, a rs485 comms protocol (used by a home automation controller) and several screen control routines like clear screen, cursor positioning, color and palette changes, line drawing routines, etc. The card is set in medium resolution graphics mode and the character size gives me a screen of 32 chars wide x 14 high. It has been a lot of fun to make and use. Using a VGA card could probably be done, but you would need to know all the i/o mode bits for it and would have a lot more memory i/o to do in order to get your screen image. You would obviously need to write to the raw registers and memory, the bios being useless with an 8051. |
Topic | Author | Date |
Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card | 01/01/70 00:00 | |
RE: Using an 8051 to drive a CGA card![]() | 01/01/70 00:00 |