| Sequence | Direction | Description |
|---|---|---|
FF FF | ↔ | Literal 0xFF byte |
FF 00 | → serial | RTS low |
FF 01 | → serial | RTS high |
FF 10 | → serial | DTR low |
FF 11 | → serial | DTR high |
FF C0 | → serial | Request signal report |
FF 8x | ← client | Signal report (x = 6-bit bitmask) |
| Bit | Signal |
|---|---|
| 0 | RTS |
| 1 | DTR |
| 2 | CTS |
| 3 | DSR |
| 4 | RI |
| 5 | CD |
Report byte range: 0x80–0xBF. Sent on signal change and on FF C0 request.