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jhusak
2023-01-30 15:26:48 +00:00
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@@ -6,7 +6,7 @@ This software is for use with my super simple flash cartridge (look into eagle c
The banking scheme was chosen because it is very simple to handle with 3 raw TTL chips (and two double diodes acting as triple "or" gate in version 1MB). There is probably no simplier scheme, either in application or in handling by 6502 (only one instruction needed to change bank)
The cartridge is driven by addresses D500-D580; write to D500 sets the first bank - this is default boot bank. Write to D501 sets second bank etc. The max bank is set by write to D57F; write to D580 switches off the cartridge. The banks will overlap if there are less of them than 128.
The cartridge is driven by addresses D500-D580; write to D500 sets the first bank - this is default boot bank. Write to D501 sets second bank etc. The max bank is set by write to D57F; write to D580 switches off the cartridge. The banks may have repeated contents if there are less of them than 128.
The J(atari)Cart first came in size max 256 kB (6 line flip flop); then the second version of pcb was created with 8-bit flip-flop with max capacity of 1MB.
Current Atari-programmable cartridge pcbs are gold-plated J(atari)cart1MB ones. They have two memory chip sockets available. In first socket you can place either 27c0x0 prom for read only memory (then there is no possibility to program it by Atari machine, you must use external prom programmer) or flash eeprom for read-write memory. In second socket you can place either flash or prom read only memory as well. Or nothing. The first (boot) memory can be hardware write-protected, when you want to have rom functionality in first half, but wnat to use flash memories. There is no such feature for second memory chip (always possible read/write when flash chip used).