Designing the Videopac SDCart. 1: The MCU and system bus.
Introduction We will look at the Videopac's digitial system. It is a cartridge based gaming console. The intention of these blog series is to design an SDcard interface. First I'd like to get to know the system, and I will be focusing on the signals present at the Cartridge port. System specs CPU: Intel 8048 8-bit @ 1,79 MHz Memory: RAM: 64 bytes AV-RAM: 128 bytes BIOS-ROM: 1k bytes Cartridges: 2k, 4k and 8k bytes The Intel 8048 microcontroller The videopac has a MCU with 1k bytes of BIOS ROM. 27 I/O 8-bit timer/counter Onboard oscillator/clock circuits Address latch enable (ALE) 96 instructions, 1 and 2 bytes long. The Data and address signals are transfered on the same 8-bit BUS. For each instruction fetch, the processor put the address on the BUS, latch it with the latch ALE strobe, and then read the instruction on the BUS driven by a ROM. The digital design of the Videopac The 8048 MCU has an internal rom preprogrammed with a bios. Th