DESCRIPTION OF PIN FUNCTIONS
BUFFER
QFP/
TQFP
PIN NO.
TYPE
NAME
SYMBOL
DESCRIPTION
80,90
nData Set Ready nDSR1
I
Active low Data Set Ready inputs for the serial
port. Handshake signal which notifies the
UART that the modem is ready to establish
nDSR2
the communication link.
monitor the status of nDSR signal by reading
bit 5 of Modem Status Register (MSR).
The CPU can
A
nDSR signal state change from low to high
after the last MSR read will set MSR bit 1 to a
1. If bit 3 of Interrupt Enable Register is set,
the interrupt is generated when nDSR
changes state. Note: Bit 5 of MSR is the
complement of nDSR.
85,87
nData Carrier
Detect
nDCD1
nDCD2
I
Active low Data Carrier Detect inputs for the
serial port. Handshake signal which notifies
the UART that carrier signal is detected by the
modem. The CPU can monitor the status of
nDCD signal by reading bit 7 of Modem Status
Register (MSR). A nDCD signal state change
from low to high after the last MSR read will
set MSR bit 3 to a 1. If bit 3 of Interrupt
Enable Register is set, the interrupt is
generated when nDCD changes state. Note:
Bit 7 of MSR is the complement of nDCD.
84,86
nRing Indicator
nRI1
nRI2
I
Active low Ring Indicator inputs for the serial
port. Handshake signal which notifies the
UART that the telephone ring signal is
detected by the modem. The CPU can
monitor the status of nRI signal by reading bit
6 of Modem Status Register (MSR). A nRI
signal state change from low to high after the
last MSR read will set MSR bit 2 to a 1. If bit 3
of Interrupt Enable Register is set, the
interrupt is generated when nRI changes
state. Note: Bit 6 of MSR is the complement
of nRI.
PARALLEL PORT INTERFACE
10
SMSC [ SMSC CORPORATION ]
