Intel® Core™ Ultra Series 3 Processors I/O Registers
| ID | Date | Version | Classification |
|---|---|---|---|
| 872352 | 04/14/2026 | 001 | Public |
REG MCR (MCR) – Offset 10
Modem Control Register
| Bit Range | Default | Access | Field Name and Description |
|---|---|---|---|
| 31:7 | 0h | RO | Reserved3 (Reserved3) Reserved |
| 6 | 0h | RO | SIRE (SIRE) SIR Mode Enable |
| 5 | 0h | RW | AFCE (AFCE) Auto Flow Control Enable. Writeable only when AFCE_MODE == Enabled, always |
| 4 | 0h | RO | Reserved |
| 3 | 0h | RW | OUT2 (OUT2) OUT2. This is used to directly control the user-designated Output2 (out2_n) output. The value written to this location is inverted and driven out on out2_n, that is: 0 out2_n de-asserted (logic 1) 1 out2_n asserted (logic 0) Note that in Loopback mode (MCR[4] set to 1), the out2_n output is held inactive high while the value of this location is internally looped back to an input. |
| 2 | 0h | RW | OUT1 (OUT1) OUT1. This is used to directly control the user-designated Output1 (out1_n) output. The value written to this location is inverted and driven out on out1_n, that is: 0 out1_n de-asserted (logic 1) 1 out1_n asserted (logic 0) Note that in Loopback mode (MCR[4] set to 1), the out1_n output is held inactive high while the value of this location is internally looped back to an input. |
| 1 | 0h | RW | RTS (RTS) Request to Send. This is used to directly control the Request to Send (rts_n) output. |
| 0 | 0h | RW | DTR (DTR) Data Terminal Ready. This is used to directly control the Data Terminal Ready (dtr_n) output. The value written to this location is inverted and driven out on dtr_n, that is: 0 dtr_n de-asserted (logic 1) 1 dtr_n asserted (logic 0) The Data Terminal Ready output is used to inform the modem or data set that the UART is ready to establish communications. |