UM10413
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
105 of 268
NXP Semiconductors
UM10413
MPT612 User manual
15.3.9 UART1 Modem control register (U1MCR - 0xE001 0010)
The U1MCR enables the modem loopback mode and controls the modem output signals.
15.3.9.1
Auto-flow control
If auto-RTS mode is enabled, the UART1‘s receiver FIFO hardware controls the RTS1
output of the UART1. If the auto-CTS mode is enabled, the UART1‘s U1TSR hardware
only starts transmitting if the CTS1 input signal is asserted.
Auto-RTS:
The auto-RTS function is enabled by setting bit RTSen. Auto-RTS data flow
control originates in the U1RBR module and is linked to the programmed receiver FIFO
trigger level. If auto-RTS is enabled, the data-flow is controlled as follows:
6
Break Control
0
disable break transmission
0
1
enable break transmission. Output pin UART1 TXD forced to
logic 0 when U1LCR[6] is active HIGH.
7
Divisor Latch
Access Bit (DLAB)
0
disable access to divisor latches
0
1
enable access to divisor latches
Table 110. UART1 Line control register (U1LCR - address 0xE001 000C) bit description
…continued
Bit
Symbol
Value
Description
Reset value
Table 111. UART1 Modem control register (U1MCR - address 0xE001 0010) bit description
Bit
Symbol
Value
Description
Reset value
0
DTR Control
-
source for modem output pin DTR. Reads as logic 0 when
modem loopback mode is active.
0
1
RTS Control
-
source for modem output pin RTS. Reads as logic 0 when
modem loopback mode is active.
0
3:2
-
-
reserved, user software must not write logic 1s to reserved
bits; value read from a reserved bit is not defined
n/a
4
Loopback Mode
Select
modem loopback mode provides a mechanism to perform
diagnostic loopback testing. Serial data from transmitter is
connected internally to serial input of receiver. Input pin RXD1
has no effect on loopback, and output pin TXD1 is held in
marking state. Modem inputs (CTS, DSR, RI and DCD) are
disconnected externally. Externally, modem outputs (RTS,
DTR) are set inactive. Internally, four modem outputs are
connected to four modem inputs. Therefore, upper 4 bits of
U1MSR are driven by the lower 4 bits of U1MCR rather than
the 4 modem inputs in normal mode. Permits modem status
interrupts to be generated in loopback mode by writing lower 4
bits of U1MCR.
0
0
disable modem loopback mode
1
enable modem loopback mode
5:3
-
-
reserved, user software must not write logic 1s to reserved
bits; value read from a reserved bit is not defined
n/a
6
RTSen
auto-RTS control bit
0
0
disable auto-RTS flow control
1
enable auto-RTS flow control
7
CTSen
auto-CTS control bit
0
0
disable auto-CTS flow control
1
enable auto-CTS flow control