A byte of I/O processor memory may be read or written across the Tube using this call. A 32 bit address should be contained in memory at the address contained in the X and Y registers.
For writes (OSWord 0x06) the value to write should be placed in XY+4
For reads (OSWord 0x05) the value read is placed in XY+4 on exit.
Parameter block
| XY+ | Content | Read call | Write call |
|---|---|---|---|
| 0 | LSB of address in I/O processor | ||
| 1 | |||
| 2 | |||
| 3 | MSB of address in I/O processor | ||
| 4 | Byte read by OSWord 0x05 | Byte to write with OSWord 0x06 |
If the I/O processor uses 16 bit memory addressing only least significant two bytes need to be specified.