| FADF || Channel B control || Channel B control
|-
| FBDC || 8253 Load counter 0 || 8253 Read counter 0
|-
| FBDD || 8253 Load counter 1 || 8253 Read counter 1
|-
| FBDE || 8253 Load counter 2 || 8253 Read counter 2
|-
| FBDF || Write mode word || -