==== RS232 I/O Ports ====
The RS232-C interface of the -XRS modules are suspected were advertised to be at least partially compatible with Amstrad/Pace interfaces, but have only one channel (no channel B).
* [[Media:Vortex RS232-C Manual.pdf|Vortex RS232-C Manual]] {{DE}} (pdf)
{| class="wikitable"
|-
! Address !! Read !! WriteDescription
|-
| 0xFADC || Channel A data || Channel A SIO data(R/W)
|-
| 0xFADD || Channel A control || Channel A SIO control(R/W)
|-
| 0xFADE 0xFBDC || Channel B data || Channel B data8253 counter 0 (R/W)
|-
| 0xFADF 0xFBDD || Channel B control || Channel B control8253 counter 1 (R/W)
|-
| 0xFBDC || 8253 Load counter 0 || 8253 Read counter 0|-| 0xFBDD || 8253 Load counter 1 || 8253 Read counter 1|-| 0xFBDE || 8253 Load counter 2 || 8253 Read counter 2|-| 0xFBDF || Write mode Mode word || -(W)
|}