UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
291 of 515
NXP Semiconductors
UM11029
Chapter 17: LPC84x USART0/1/2/3/4
17.6.1 USART Configuration register
The CFG register contains communication and mode settings for aspects of the USART
that would normally be configured once in an application.
Remark:
If software needs to change configuration values, the following sequence should
be used: 1) Make sure the USART is not currently sending or receiving data. 2) Disable
the USART by writing a 0 to the Enable bit (0 may be written to the entire register). 3)
Write the new configuration value, with the ENABLE bit set to 1.
Table 323. USART Configuration register (CFG, address 0x4006 4000 (USART0), 0x4006 8000
(USART1), 0x4006 C000 (USART2), 0x4007 0000 (USART3), 0x4007 4000
(USART4)) bit description
Bit
Symbol
Value Description
Reset
Value
0
ENABLE
USART Enable.
0
0
Disabled. The USART is disabled and the internal state
machine and counters are reset. While Enable = 0, all
USART interrupts and DMA transfers are disabled. When
Enable is set again, CFG and most other control bits remain
unchanged. For instance, when re-enabled, the USART will
immediately generate a TXRDY interrupt (if enabled in the
INTENSET register) or a DMA transfer request because the
transmitter has been reset and is therefore available.
1
Enabled. The USART is enabled for operation.
1
-
Reserved. Read value is undefined, only zero should be
written.
NA
3:2
DATALEN
Selects the data size for the USART.
00
0x0
7 bit Data length.
0x1
8 bit Data length.
0x2
9 bit data length. The 9th bit is commonly used for
addressing in multidrop mode. See the ADDRDET bit in the
CTL register.
0x3
Reserved.
5:4
PARITYSEL
Selects what type of parity is used by the USART.
00
0x0
No parity.
0x1
Reserved.
0x2
Even parity. Adds a bit to each character such that the
number of 1s in a transmitted character is even, and the
number of 1s in a received character is expected to be even.
0x3
Odd parity. Adds a bit to each character such that the
number of 1s in a transmitted character is odd, and the
number of 1s in a received character is expected to be odd.
6
STOPLEN
Number of stop bits appended to transmitted data. Only a
single stop bit is required for received data.
0
0
1 stop bit.
1
2 stop bits. This setting should only be used for
asynchronous communication.
8:7
-
Reserved. Read value is undefined, only zero should be
written.
NA