VRAM address should only be set on successful register write pair

[nrivard]

VRAM address should only be set on successful register write pair

[nrivard]

Locally, I have solved for this by adding a new field in the VDP struct:

    /// if kVDPUnsetAddr (0xFFFF), register is in "reset" mode.
    /// if any other value, it is waiting for a value pair to complete the register write process
    uint16_t registerValue;

and my register write function:

void VDPWriteToRegister(VideoDisplayProcessorRef vdp, uint8_t value) {
    if (!vdp) {
        return;
    }

    if (vdp->registerValue == kVDPUnsetAddr) {
        vdp->registerValue = value;
    } else {
        if (value & kVDPRegisterWriteMask) {
            // register write
            vdp->registers[value & (kVDPRegisterCount - 1)] = vdp->registerValue & 0xFF;
        } else {
            // vram address
            vdp->vramAddr = ((value & (kVDPVramWriteMask - 1)) << 8) | vdp->registerValue;
        }

        vdp->registerValue = kVDPUnsetAddr;
    }
}

Technically there's one more thing to do here, but I will write another issue for that 😄

[visrealm]

Closed as fixed with commit 56b100c