SC16C750 Philips Semiconductors, SC16C750 Datasheet - Page 26

• Manufacturer Part Number: SC16C750
• Description: Universal Asynchronous Receiver/Transmitter (UART) with 64-byte FIFO
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 11623
Product data
7.8 Modem Status Register (MSR)
Table 19:
This register provides the current state of the control interface signals from the
modem, or other peripheral device to which the SC16C750 is connected. Four bits of
this register are used to indicate the changed information. These bits are set to a
logic 1 whenever a control input from the modem changes state. These bits are set to
a logic 0 whenever the CPU reads this register.
Table 20:
Bit
0
Bit
7
6
5
4
3
2
Symbol
LSR[0]
Symbol
MSR[7]
MSR[6]
MSR[5]
MSR[4]
MSR[3]
MSR[2]
Line Status Register bits description
Modem Status Register bits description
Description
Receive data ready.
Rev. 04 — 20 June 2003
Description
Data Carrier Detect. DCD (Active-HIGH, logical 1). Normally this bit is
the complement of the DCD input. In the loop-back mode this bit is
equivalent to the OUT2 bit in the MCR register.
Ring Indicator. RI (Active-HIGH, logical 1). Normally this bit is the
complement of the RI input. In the loop-back mode this bit is equivalent
to the OUT1 bit in the MCR register.
Data Set Ready. DSR (Active-HIGH, logical 1). Normally this bit is the
complement of the DSR input. In loop-back mode this bit is equivalent to
the DTR bit in the MCR register.
Clear To Send. CTS. CTS functions as hardware flow control signal input
if it is enabled via EFR[7]. Flow control (when enabled) allows starting
and stopping the transmissions based on the external modem CTS
signal. A logic 1 at the CTS pin will stop SC16C750 transmissions as
soon as current character has finished transmission. Normally MSR[4] is
the complement of the CTS input. However, in the loop-back mode, this
bit is equivalent to the RTS bit in the MCR register.
DCD
RI
Logic 0 = No data in receive holding register or FIFO (normal default
condition).
Logic 1 = Data has been received and is saved in the receive holding
register or FIFO.
Logic 0 = No DCD change (normal default condition).
Logic 1 = The DCD input to the SC16C750 has changed state since
the last time it was read. A modem Status Interrupt will be generated.
Logic 0 = No RI change (normal default condition).
Logic 1 = The RI input to the SC16C750 has changed from a logic 0 to
a logic 1. A modem Status Interrupt will be generated.
[1]
[1]
…continued
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
UART with 64-byte FIFO
SC16C750
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