DESCRIPTION OF PIN FUNCTIONS
BUFFER
PIN NO.
NAME
SYMBOL
TYPE
DESCRIPTION
84,86 nRing Indicator
nRI1, nRI2
I
Active low Ring Indicator input for primary
and secondary serial ports. 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.
94
Drive 2
nADRx
DRV2
I
In PS/2 mode, this input indicates whether a
second drive is connected; DRV2 should be
low if a second drive is connected. This
status is reflected in a read of Status
Register
A.
(Only
available
in
FDC37C665GT.
This pin must not be
driven in the FDC37C666GT)
nADRx
O24
Optional I/O port address decode output.
Refer to Configuration registers CR3, CR8
and CR9 for more information. Active low.
(Available
in
FDC37C665GT
and
FDC37C666GT.) Defaults to tri-state after
power-up. This pin has a 30ma internal pull-
up.
Parallel Port
Interrupt
Request 2
PINTR2
ECPEN
O24
This interrupt from the Parallel Port is
enabled/disabled via bit 4 of the Parallel
Port Control Register.
Refer to
configuration registers CR1 and CR3 for
more information.
I
FDC37C666GT (Adapter Mode): Enhanced
Parallel Port mode select. Refer to
FDC37C666GT hardware configuration for
more information. Read and latched during
reset active.
PARALLEL PORT INTERFACE
13
SMSC [ SMSC CORPORATION ]
