Tandy 200 RAM

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This page captures some useful information for programming with T200 RAM.

T200 RAM selection

T200 RAM is always 24k blocks, from A000 to FFFF. There can be any number of banks from 1 to 3.

In the T200 memory map, there are 6 defined blocks - 3 ROM and 3 RAM. Bank selection is accomplished by writing to IO port D8 (216). The current setting of the bank selection may be read back from D8 also.

Bit 1,0 --> selection of ROM bank (0000-9FFF or 0000-7FFF) 00 = main ROM (40k) 01 = multiplan (32k) 10 = option ROM (if installed)

Bit 3,2 --> selection of RAM bank (A000-FFFF) 00 = bank 1 01 = bank 2 (if installed) 10 = bank 3 (if installed)

Register D8 can be written at any time, with catastrophic results if not done correctly!

I believe there are rom routines for bank to bank copy or reads, but I can't find them currently.


ALTLCD

ALTLCD exists in all 3 RAM banks, and is 640 bytes long, running from F7B0 (63408) to FA2F (64047).

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