SC16C754B NXP Semiconductors, SC16C754B Datasheet - Page 28

• Manufacturer Part Number: SC16C754B
• Description: 5 V - 3.3 V and 2.5 V quad UART - 5 Mbit/s (max.)
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SC16C754B_4
Product data sheet
7.7 Modem Status Register (MSR)
This 8-bit register provides information about the current state of the control lines from the
modem, data set, or peripheral device to the processor. It also indicates when a control
input from the modem changes state.
per channel.
Table 15.
[1]
Bit
7
6
5
4
3
2
1
0
The primary inputs RI, CD, CTS, DSR are all active LOW, but their registered equivalents in the MSR and
MCR (in loopback) registers are active HIGH.
Symbol
MSR[7]
MSR[6]
MSR[5]
MSR[4]
MSR[3]
MSR[2]
MSR[1]
MSR[0]
Modem status register bits description
[1]
[1]
[1]
[1]
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
Description
CD (active HIGH, logic 1). This bit is the complement of the CD input during
normal mode. During internal loopback mode, it is equivalent to MCR[3].
RI (active HIGH, logic 1). This bit is the complement of the RI input during
normal mode. During internal loopback mode, it is equivalent to MCR[2].
DSR (active HIGH, logic 1). This bit is the complement of the DSR input
during normal mode. During internal loopback mode, it is equivalent MCR[0].
CTS (active HIGH, logic 1). This bit is the complement of the CTS input
during normal mode. During internal loopback mode, it is equivalent to
MCR[1].
state. Cleared on a read.
from LOW to HIGH. Cleared on a read.
state. Cleared on a read.
state. Cleared on a read.
CD. Indicates that CD input (or MCR[3] in loopback mode) has changed
RI. Indicates that RI input (or MCR[2] in loopback mode) has changed state
DSR. Indicates that DSR input (or MCR[0] in loopback mode) has changed
CTS. Indicates that CTS input (or MCR[1] in loopback mode) has changed
Rev. 04 — 6 October 2008
Table 15
shows modem status register bit settings
SC16C754B
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