UM10462 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2016. All rights reserved.
User manual Rev. 5.5 — 21 December 2016 256 of 523
NXP Semiconductors
UM10462
Chapter 12: LPC11U3x/2x/1x USART
12.5.12 USART Auto-baud Control Register
The USART Auto-baud Control Register (ACR) controls the process of measuring the
incoming clock/data rate for baud rate generation, and can be read and written at the
user’s discretion.
12.5.12.1 Auto-baud
The USART auto-baud function can be used to measure the incoming baud rate based on
the “AT” protocol (Hayes command). If enabled the auto-baud feature will measure the bit
time of the receive data stream and set the divisor latch registers DLM and DLL
accordingly.
Auto-baud is started by setting the ACR Start bit. Auto-baud can be stopped by clearing
the ACR Start bit. The Start bit will clear once auto-baud has finished and reading the bit
will return the status of auto-baud (pending/finished).
Table 244. Auto-baud Control Register (ACR - address 0x4000 8020) bit description
Bit Symbol Value Description Reset
value
0 START This bit is automatically cleared after auto-baud
completion.
0
0 Auto-baud stop (auto-baud is not running).
1 Auto-baud start (auto-baud is running). Auto-baud run
bit. This bit is automatically cleared after auto-baud
completion.
1 MODE Auto-baud mode select bit. 0
0 Mode 0.
1 Mode 1.
2AUTORESTART Start mode 0
0 No restart
1 Restart in case of time-out (counter restarts at next
USART Rx falling edge)
7:3 - Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
0
8 ABEOINTCLR End of auto-baud interrupt clear bit (write only
accessible).
0
0 Writing a 0 has no impact.
1 Writing a 1 will clear the corresponding interrupt in the
IIR.
9 ABTOINTCLR Auto-baud time-out interrupt clear bit (write only
accessible).
0
0 Writing a 0 has no impact.
1 Writing a 1 will clear the corresponding interrupt in the
IIR.
31:10 - Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
0
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