| Name | Type | Description | Default |
|---|---|---|---|
| -b location | I/O address | I/O Location. | none |
| -1 | Access a one byte (8 bit) I/O location. Only the 8 least significant bits of value will be used | -1 | |
| -2 | Access a two byte (16 bit) I/O location. Only the 16 least significant bits of value will be used | -1 | |
| -4 | Access a one word (32 bit) I/O location. | -1 |