Post by dshadoff on Aug 8, 2020 0:53:48 GMT
I apparently don't have enough projects to keep me busy, so I started looking at the FX-BMP cartridge... wow, that has become an expensive item ($100US and up !).
I was hoping to learn more about the cartridge port pinout and the possibility of being able to boot from it.
I wasn't able to find any pinouts on the internet, so I looked inside. The contents include:
- a 128Kx8 Static RAM chip
- a custom ASIC (or possibly CPLD)
- a supercap
- a battery compartment
- some circuitry with several SOT-23 devices (not sure whether these are MOSFETs/BJTs/something else) and other passives, and a SOT-89 (voltage regulator probably).
The SRAM's Address and Data lines, and also /WE (write enable) are connected directly to the card edge, but the chip select and /OE (output enable) lines are not. While my first suspicion was that the ASIC decodes these lines, I haven't trace the lines yet.
I suspect that the ASIC has a more complex function than just enabling these... so I am asking whether anybody here knows how the external cartridge backup memory is interrogated at boot (or memory management program access) time ?
- For example, does the ASIC respond to an "interrogation" command set ?
- Does the memory need to be "enabled" like the Tennokoe 2 device ?
I was able to find an additional source for programming information here - and it indicates that the backup memory cartridge should be bootable media:
matejhorvat.si/en/pcfx/index.htm
This document indicates that the backup port is memory-mapped, so this is good information.
I had considered making one or more of the following devices:
- homemade backup cartridge (SRAM)
- homemade backup cartridge (non-volatile)
- cartridge reader for computer backup/restore
- development cartridge
...Just wanted to share information if anybody had gone down this road before.
Dave
I was hoping to learn more about the cartridge port pinout and the possibility of being able to boot from it.
I wasn't able to find any pinouts on the internet, so I looked inside. The contents include:
- a 128Kx8 Static RAM chip
- a custom ASIC (or possibly CPLD)
- a supercap
- a battery compartment
- some circuitry with several SOT-23 devices (not sure whether these are MOSFETs/BJTs/something else) and other passives, and a SOT-89 (voltage regulator probably).
The SRAM's Address and Data lines, and also /WE (write enable) are connected directly to the card edge, but the chip select and /OE (output enable) lines are not. While my first suspicion was that the ASIC decodes these lines, I haven't trace the lines yet.
I suspect that the ASIC has a more complex function than just enabling these... so I am asking whether anybody here knows how the external cartridge backup memory is interrogated at boot (or memory management program access) time ?
- For example, does the ASIC respond to an "interrogation" command set ?
- Does the memory need to be "enabled" like the Tennokoe 2 device ?
I was able to find an additional source for programming information here - and it indicates that the backup memory cartridge should be bootable media:
matejhorvat.si/en/pcfx/index.htm
This document indicates that the backup port is memory-mapped, so this is good information.
I had considered making one or more of the following devices:
- homemade backup cartridge (SRAM)
- homemade backup cartridge (non-volatile)
- cartridge reader for computer backup/restore
- development cartridge
...Just wanted to share information if anybody had gone down this road before.
Dave