OM13008,598 NXP Semiconductors, OM13008,598 Datasheet - Page 144

• Manufacturer Part Number: OM13008,598
• Description: BOARD LPC XPRESSO LPC122X
• Manufacturer: NXP Semiconductors
• Series: LPCXpressor

Specifications of OM13008,598

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-6642; OM13008

NXP Semiconductors
UM10441
User manual
9.5.8.1.1 Auto-RTS
9.5.8.1 Auto-flow control
Table 147. UART Modem Control Register (MCR - address 0x4000 8010) bit description
If auto-RTS mode is enabled the UART receiver FIFO hardware controls the RTS output
of the UART. If the auto-CTS mode is enabled the UART TSR hardware will only start
transmitting if the CTS input signal is asserted.
The auto-RTS function is enabled by setting the RTSen bit. Auto-RTS data flow control
originates in the RBR module and is linked to the programmed receiver FIFO trigger level.
If auto-RTS is enabled, the data-flow is controlled as follows:
When the receiver FIFO level reaches the programmed trigger level, RTS is deasserted
(to a high value). It is possible that the sending UART sends an additional byte after the
trigger level is reached (assuming the sending UART has another byte to send) because it
might not recognize the deassertion of RTS until after it has begun sending the additional
byte. RTS is automatically reasserted (to a low value) once the receiver FIFO has reached
the previous trigger level. The reassertion of RTS signals to the sending UART to continue
transmitting data.
Bit
0
1
3:2
4
5
6
7
31:8 -
Symbol
DTRCTR
L
RTSCTR
L
-
LMS
-
RTSEN
CTSEN
All information provided in this document is subject to legal disclaimers.
Value Description
0
1
0
1
0
1
-
Rev. 1.1 — 10 March 2011
Source for modem output pin DTR. This bit reads as 0 when
modem loopback mode is active.
Source for modem output pin RTS. This bit reads as 0 when
modem loopback mode is active.
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
Loopback Mode Select. The modem loopback mode provides a
mechanism to perform diagnostic loopback testing. Serial data
from the transmitter is connected internally to serial input of the
receiver. Input pin, RXD, has no effect on loopback and output
pin, TXD is held in marking state. The DSR, CTS, DCD, and RI
pins are ignored. Externally, DTR and RTS are set inactive.
Internally, the upper four bits of the MSR are driven by the lower
four bits of the MCR. This permits modem status interrupts to be
generated in loopback mode by writing the lower four bits of
MCR.
Disable modem loopback mode.
Enable modem loopback mode.
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
RTS enable
Disable auto-rts flow control.
Enable auto-rts flow control.
CTS enable
Disable auto-cts flow control.
Enable auto-cts flow control.
Reserved
Chapter 9: LPC122x UART0 with modem control
UM10441
© NXP B.V. 2011. All rights reserved.
144 of 442
Reset
value
0
0
0
0
0
0
0
-