UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
295 of 515
NXP Semiconductors
UM11029
Chapter 17: LPC84x USART0/1/2/3/4
17.6.3 USART Status register
The STAT register primarily provides a complete set of USART status flags for software to
read. Flags other than read-only flags may be cleared by writing ones to corresponding
bits of STAT. Interrupt status flags that are read-only and cannot be cleared by software,
can be masked using the INTENCLR register (see
).
The error flags for received noise, parity error, framing error, and overrun are set
immediately upon detection and remain set until cleared by software action in STAT.
9
CLRCCONRX
Clear Continuous Clock.
0
0
No effect on the CC bit.
1
Auto-clear. The CC bit is automatically cleared when a
complete character has been received. This bit is cleared
at the same time.
15:10 -
Reserved. Read value is undefined, only zero should be
written.
NA
16
AUTOBAUD
Autobaud enable.
0
0
Disabled. UART is in normal operating mode.
1
Enabled. UART is in autobaud mode. This bit should only
be set when the UART is enabled in the CFG register and
the UART receiver is idle. The first start bit of RX is
measured and used the update the BRG register to match
the received data rate. AUTOBAUD is cleared once this
process is complete, or if there is an ABERR. This bit can
be cleared by software when set, but only when the UART
receiver is idle. Disabling the UART in the CFG register
also clears the AUTOBAUD bit.
31:17 -
Reserved. Read value is undefined, only zero should be
written.
NA
Table 324. USART Control register (CTL, address 0x4006 4004 (USART0), 0x4006 8004
(USART1), 0x4006 C004 (USART2), 0x4007 0004 (USART3), 0x4007 4004
(USART4)) bit description
…continued
Bit
Symbol
Value
Description
Reset
value
Table 325. USART Status register (STAT, address 0x4006 4008 (USART0), 0x4006 8008 (USART1), 0x4006 C008
(USART2), 0x4007 0008 (USART3), 0x4007 4008 (USART4)) bit description
Bit
Symbol
Description
Reset
value
Access
0
RXRDY
Receiver Ready flag. When 1, indicates that data is available to be read from
the receiver buffer. Cleared after a read of the RXDAT or RXDATSTAT
registers.
0
RO
1
RXIDLE
Receiver Idle. When 0, indicates that the receiver is currently in the process of
receiving data. When 1, indicates that the receiver is not currently in the
process of receiving data.
1
RO
2
TXRDY
Transmitter Ready flag. When 1, this bit indicates that data may be written to
the transmit buffer. Previous data may still be in the process of being
transmitted. Cleared when data is written to TXDAT. Set when the data is
moved from the transmit buffer to the transmit shift register.
1
RO