SC16C750B Datasheet, PDF (26/44 Pages) NXP Semiconductors – 5 V, 3.3 V and 2.5 V UART with 64-byte FIFOs

Philips Semiconductors
SC16C750B
5 V, 3.3 V and 2.5 V UART with 64-byte FIFOs
Table 20: Line Status Register bits description…continued
Bit Symbol Description
0
LSR[0] Receive data ready.
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.
7.8 Modem Status Register (MSR)
This register provides the current state of the control interface signals from the
modem, or other peripheral device to which the SC16C750B 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 21: Modem Status Register bits description
Bit Symbol Description
7
MSR[7] 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.
6
MSR[6] 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.
5
MSR[5] 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.
4
MSR[4] 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 SC16C750B 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.
3
MSR[3] ∆DCD ^[1]
Logic 0 = No DCD change (normal default condition).
Logic 1 = The DCD input to the SC16C750B has changed state since
the last time it was read. A modem Status Interrupt will be generated.
2
MSR[2] ∆RI ^[1]
Logic 0 = No RI change (normal default condition).
Logic 1 = The RI input to the SC16C750B has changed from a logic 0
to a logic 1. A modem Status Interrupt will be generated.
9397 750 14453
Product data
Rev. 03 — 13 December 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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