On Wed, 26 Apr 2000, Maarten ter Huurne wrote:
> This may be a serious one:
> "The on-chip register addresses are located in the I/O address space from
> 0000H to 00FFH (16-bit I/O addresses). In order to access the on-chip I/O
> registers (using I/O instruction), the high-order 8 bits of the 16-bit I/O
> address must be 0."
> This means the MSX I/O ports will be inaccessable if the high-order 8 bits
> happen to be zero. Those high-order bits come from one of the registers,
> right? I thought it was B, but Laurens said A. Anyway, the value of that
> register is unknown in MSX programs.
I read some more:
"The internal I/O registers of the AB180-20 occupy the 64 addresses
between 00h and 3Fh on reset. To avoid conflicts with external devices
these registers can be relocated within the bottom 256 bytes of the I/O
address space."
Are there any important MSX devices with I/O addresses in that range? I
know the music module has some to access its sample interface. But that's
not such a big deal for me.
Bye,
Maarten
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