PC87307 datasheet(20/218 Pages) NSC

20 / 218 page

Signal/Pin Connection and Description

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POR

159

APC

Output

Group 21

Power Off Request – This signal becomes active when an APC

Switch Off event occurs, regardless of the fail-safe delay. Selection of

edge or level for POR is via the APCR1 register of the APC.

Selection of an output buffer is via GPIO22 output buffer control bits

(in the Port 2 Output Type and Port 2 Pull-up Control registers

described in Table 8-1 on page 170). See Section 4.3 on page 55.

This signal is multiplexed with GPIO22.

ISA-Bus

Input

Group 1

I/O Read – An active low RD input signal indicates that the

microprocessor has read data.

RDATA

FDC

Input

Group 1

Read Data – This input signal holds raw serial data read from the

Floppy Disk Drive (FDD).

RI2,1

145, 135

UART1, APC

Input

Group 7

Ring Indicators (Modem) – When low, this signal indicates that a

telephone ring signal has been received by the modem.

The CPU can test the status of the RI modem status input signal 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 signal has

changed from low to high since the previous reading of the MSR.

When the TERI bit of the MSR is set, an interrupt is generated if

modem status interrupts are enabled.

When enabled, a high to low transition on RI1 or RI2 activates the

ONCTL pin. The RI1 and RI2 pins each have an schmitt-trigger input

buffer.

RING

69 or 160

APC

Input

Group 7

Ring Indicator (APC) – Detection of an active low RING pulse or

pulse train activates the ONCTL signal. The APC’s APCR2 register

determines which pin the RING signal uses. The pins have a schmitt-

trigger input buffer.

RING is multiplexed on pin 69 with XDCS and on pin 160 with

GPIO23.

RTS2,1

146, 136

UART1,

UART2

Output

Group 17

Request to Send – When low, these output signals indicate to the

modem or other data transfer device that the corresponding UART1

or UART2 is ready to exchange data.

The RTS signal can be set active low by programming bit 1 (RTS) of

the Modem Control Register (MCR) to a high level. A Master Reset

(MR) sets RTS to inactive high. Loopback operation holds it inactive.

RTS2 is multiplexed with CFG2. RTS1 is multiplexed with BADDR1.

SELCS

Conﬁguration

Input

Group 4

Select CSOUT – During reset, this signal is sampled into bit 1 of the

SuperI/O Conﬁguration 1 register (index 21h).

A 40 K

Ω internal pull-up resistor (or a 10 KΩ external pull-down

resistor for National Semiconductor testing) controls this pin during

reset. Do not pull this signal low during reset.

This signal is multiplexed with GPIO21, IRSL2 and XD6.

SIN2,1

147, 137

UART1,

UART2

Input

Group 1

Serial Input – This input signal receives composite serial data from

the communications link (peripheral device, modem or other data

transfer device.)

SLCT

114

Parallel Port

Input

Group 2

Select – This input signal is set active high by the printer when the

printer is selected. This pin is internally connected to a nominal

25 K

Ω pull-down resistor.

SLIN

118

Parallel Port

I/O

Group 13

Select Input – When this signal is active low it selects the printer.

This signal is in TRI-STATE after a 0 is loaded into the corresponding

control register bit.

An external 4.7 K

Ω pull-up resistor should be used.

This signal is multiplexed with ASTRB.

Signal/Pin

Name

Number

Module

I/O and

Group #

Function

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