sc16c554dbib64 NXP Semiconductors, sc16c554dbib64 Datasheet - Page 36

• Manufacturer Part Number: sc16c554dbib64
• Description: 5 V, 3.3 V And 2.5 V Quad Uart, 5 Mbit/s Max. With 16-byte Fifos
• Manufacturer: NXP Semiconductors

Philips Semiconductors
SC16C554B_554DB_3
Product data sheet
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 SC16C554B/554DB 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:
[1]
Bit
7
6
5
4
3
2
1
0
Whenever any MSR[3:0] is set to logic 1, a Modem Status Interrupt will be generated.
Symbol
MSR[7]
MSR[6]
MSR[5]
MSR[4]
MSR[3]
MSR[2]
MSR[1]
MSR[0]
Modem Status Register bits description
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 16-byte FIFOs
Description
CD (active HIGH, logical 1). Normally this bit is the complement of the CD
input. In the Loop-back mode this bit is equivalent to the OP2 bit in the MCR
register.
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 OP1 bit in the MCR
register.
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.
CTS (active HIGH, logical 1). CTS functions as hardware flow control signal
input if it is enabled via MCR[5]. 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 SC16C554B/554DB 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.
CD
RI
DSR
CTS
Rev. 03 — 1 September 2005
Logic 0 = No CD change (normal default condition).
Logic 1 = The CD input to the SC16C554B/554DB 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 SC16C554B/554DB has changed from a
logic 0 to a logic 1. A modem Status Interrupt will be generated.
Logic 0 = No DSR change (normal default condition).
Logic 1 = The DSR input to the SC16C554B/554DB has changed state
since the last time it was read. A modem Status Interrupt will be
generated.
Logic 0 = No CTS change (normal default condition).
Logic 1 = The CTS input to the SC16C554B/554DB has changed state
since the last time it was read. A modem Status Interrupt will be
generated.
[1]
[1]
[1]
[1]
SC16C554B/554DB
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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