Ben-kenobi escribió: ↑02 Sep 2018, 13:00
Expansion interna? Va sobre el zocalo del z80?
Si tienes los gerves o vas a pedir placa me interesaria.
Si, interna, pero va conectada al PAL del 6128 (o eso segun CPCWiki porqué no cuadra con lo que explica luego Yarek en su página)...
http://www.cpcwiki.eu/index.php/CPC4MB.
No tengo pensado hacer nada sin antes no tener un mínimo de fiablidad que funciona bien.
El caso es que no conozco a nadie que lo haya montado y su autor dejó de dar señales de vida...
Edito: Tambien va un módulo al Z80. Son tres pcbs y una de ellas va en el socket del Z80. Aquí se puede ver claramente la instalación:
Y por lo que veo las otras 2 pcbs sustituyen un banco de RAM ICs 4164...y van conectados a algun 74LS, haciendo que el CPC pueda "ver" 64 bancos de 64kb cada uno.
Cita de su web:
"Upgrade is made of 3 boards, one separate logic chip and OR gate made from 2 NPN transistors and resistor. Two boards replace bank 2 and contain 4MB DRAM. The third one is mounted under Z80 and handles switching of 64 banks. Boards are connected with 2×3 wires.
Control signals for new memory: /RAS1' and /CAS1' are generated from control signals for bank 2: /RAS1 and /CAS1.
The 74LS153 generates two signals. One is /CAS1', used to access the memory and for refreshment. Second is /244, used to open 74LS244 buffer while writing.
The /CAS1' is low in Z80CPU refreshment cycles (/RFSH=0). While writing to new RAM, the falling edge of /CAS1' is delayed by 80-100ns to /CAS1 generated by PAL chip, because must wait for /WE line to be set low. While reading the dealy doesn't matter.
The /244 opens 74LS244 buffer also while memory writing (/CAS1=0 and /WE=0). This is done because the new memory doesn't have separate input and output of data lines as 4164 chips.
The OR gate made from 2 NPN transistors and resistor forces high stateon /RAS1' when /RAS=1 or /MREQ=1. While reading and writing to memory the /MREQ is 0 and only /RAS matters. But /MREQ=1 forces /RAS1' to be high in refresh cycles, so together with /CAS1' generation this makes correct CBR refreshement."
