UM10562 Datasheet, PDF (524/942 Pages) NXP Semiconductors – LPC408x/407x User manual

NXP Semiconductors
UM10562
Chapter 19: LPC408x/407x UART4
19.6.10 UART4 Auto-baud Control Register
The UART4 Auto-baud Control Register (U4ACR) controls the process of measuring the
incoming clock/data rate for the baud rate generation and can be read and written at
user’s discretion.
Table 419: UART4 Auto-baud Control Register (ACR - 0x400A 4020) bit description
Bit Symbol
Value Description
Reset value
0
START
Start bit. 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.
2
AUTORESTART
Restart bit.
0
0 No restart.
1 Restart in case of time-out (counter restarts at next UARTn Rx falling
0
edge)
7:3 -
Reserved. Read value is undefined, only zero should be written.
NA
8
ABEOINTCLR
End of auto-baud interrupt clear bit (write-only accessible). Writing a 1 will
0
clear the corresponding interrupt in the UnIIR. Writing a 0 has no impact.
0 No impact.
1 Clear the corresponding interrupt in the IIR.
9
ABTOINTCLR
Auto-baud time-out interrupt clear bit (write-only accessible). Writing a 1
0
will clear the corresponding interrupt in the UnIIR. Writing a 0 has no
impact.
0 No impact.
1 Clear the corresponding interrupt in the IIR.
31:10 -
Reserved. Read value is undefined, only zero should be written.
NA
19.6.10.1 Auto-baud
The UART4 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 U4DLM and U4DLL
accordingly.
Remark: the fractional rate divider is not connected during auto-baud operations, and
therefore should not be used when the auto-baud feature is needed.
Auto-baud is started by setting the U4ACR Start bit. Auto-baud can be stopped by clearing
the U4ACR 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).
UM10562
User manual
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 13 September 2012
© NXP B.V. 2012. All rights reserved.
524 of 942