Acer Extensa 61X Service Manual page 142

Table 2-14 NS87336VJG Pin Descriptions (continued)
Pin No.
/RI1 68, 60
/RI2
/RTS1 72, 64
/RTS2
SIN1 73, 65
SIN2
SIRQ1 58,
SIRQ2 49,
SIRQ4 47
SLCT 80
/SLIN 79
SOUT1 71, 63
SOUT2
/STB 93
/STEP 38
(Normal Mode)
/STEP 79
(PPM Mode)
Major Chips Description
I/O Description
I UARTs Ring Indicator. When low, this indicates that a telephone ring
signal has been received by the modem. The /RI signal is a modem
status input whose condition is tested by the CPU by reading bit 6
(RI) of the Modem Status Register (MSR) for the appropriate serial
channel. Bit 6 is the complement of the RI signal. Bit 2 ( TERI) of
the MSR indicates whether the RI input has changed from low to high
since the previous reading of the MSR.
NOTE: When the TERI bit of the MSR is set and Modem Status
interrupts are enabled, an interrupt is generated.
O UARTs Request to Send. When low, this output indicates to the
modem or data set that the UART is ready to exchange data. The
RTS signal can be set to an active low by programming bit 1 (RTS) of
the Modem Control Register to a high level.
operation sets this signal to its inactive (high) state. Loop mode
operation holds this signal to its inactive state.
I UARTs Serial Input. This input receives composite serial data from
the communications link (peripheral device, modem, or data set).
I System interrupt 1, 2, and 3. This input can be routed to one of the
following output pins: IRQ3-IRQ7, IRQ9-IRQ12.
SIRQ13 can be also routed to IRQ15.
determines to which output pin the input pin is routed to.
SIRQ1 is multiplexed with IRQ15, SRIQ12 is multiplexed with
DRATE1/MSEN1/CS0,
DRV2/PNF/DR23.
I Parallel Port Select. This input is set high by the printer when it is
selected. This pin has a nominal 25 K
to it.
I/O Parallel Port Select Input. When this signal is low, it selects the
printer. This pin is in a tristate condition 10 ns after a 0 is loaded into
the corresponding Control Register bit. The system should pull this
pin high using a 4.7 K
O UARTs Serial Output. This output sends composite serial data to the
communications link (peripheral device, modem, or data set). The
SOUT signal is set to a marking state (logic 1) after a Master Reset
operation.
I/O Parallel Port Data Strobe. This output indicates to the printer that a
valid data is available at the printer port. This pin is in a tristate
condition 10 ns after a 0 is loaded into the corresponding Control
Register bit. The system should pull high using a 4.7 K .
O FDC Step. This output signal issues pulses to the disk drive at a
software programmable rate to move the head during a seek
operation.
O FDC Step. This pin gives an additional step signal in PPM Mode
when PNF = 0.
Software configuration
and SIRQ3 is
pull-down resistor attached
resistor.
A Master Reset
SIRQ12 and
multiplexed with
2-85