4 ms·
The previous generation of the lockout chip on the NES is also a Sharp 4-bit MCU, but even more ancient. To save gates, the chip designers made it use an LFSR p
by mips_r4300i 3y ago
The previous generation of the lockout chip on the NES is also a Sharp 4-bit MCU, but even more ancient. To save gates, the chip designers made it use an LFSR program counter. So, execution didn't go 00, 01, 02 at all. Had to be a real pain.
On the later SNES and then N64 iterations, they did use a standard incrementing PC, but still with the inscrutable opcodes. It was so arcane I had to write a special disassembler to spit out all the register operations while reversing it.
On the final (N64) iteration, these CICs actually support coexistence with multiple slave devices on the bus. They really had it down by then.