DESCRIPTION OF PIN FUNCTIONS
BUFFER
QFP/
TQFP
PIN NO.
TYPE
NAME
SYMBOL
DESCRIPTION
84,86 nRing Indicator
nRI1
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
nRI2
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
73
74
76
nPrinter Select
Input
nSLCTIN
OD24
This active low output selects the printer.
This is the complement of bit 3 of the Printer
Control Register.
Refer to Parallel Port description for use of
this pin in ECP and EPP mode.
0P24
nInitiate Output
nINIT
OD24
This output is bit 2 of the printer control
register. This is used to initiate the printer
when low.
Refer to Parallel Port description for use of
this pin in ECP and EPP mode.
0P24
nAutofeed
Output
nAUTOFD
OD24
This output goes low to cause the printer to
automatically feed one line after each line is
printed.
The nAUTOFD output is the
complement of bit 1 of the Printer Control
Register.
Refer to Parallel Port description for use of
this pin in ECP and EPP mode.
0P24
11
SMSC [ SMSC CORPORATION ]
