PC87427 datasheet(10/46 Pages) NSC

10 / 46 page

1.0 Signal/Pin Connection and Description (Continued)

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Revision 1.0

1.4.3

X-Bus Extension

1.4.4

Serial Port Interfaces (SI1, SI2 and SIM)

Signal

Pin(s)

I/O Buffer Type Power Well

Description

XRD_XEN

O6/12

VSB

Read. Active (low) level indicates a read cycle on the X-Bus.

Enable. Active (high) level indicates valid data on the X-Bus.

XWR_XRW15

O14/14

VSB

Write. Active (low) level indicates a write cycle on the X-Bus.

Read/Write. A high level indicates a read cycle on the X-Bus; a

low level indicates a write cycle on the X-Bus.

XA19_XD15

-XA12_XD8

XA11_XD7

-XA4_XD0

1-8,

24-31

I/O

INTS/O4/8

VSB

Multiplexed Data/Address Bus Lines. The XA11-4 address lines

are multiplexed with the 8-bit data lines XD7-XD0. If the 16-bit data

bus is selected, the XA19-12 address lines are multiplexed with

data lines XD15-XD8.

XA11-1,

XA0_XA20

83, 82,

55, 50,

48, 37,

21, 22,

16-18,

OO3/6

VSB

Non-Multiplexed Address Bus Lines. The XA0 address line pin

is the XA20 address line for XCSn configured to 16-bit data bus.

XSTB2-0

53,

33-34

OO3/6

VSB

Address Strobes. Controls the strobe of up to three external

latches for the multiplexed address lines.

XCS3-0

85-87,

OO14/14

VSB

Chip Selects. Controls the selection of up to four devices residing

on the X-Bus.

XRDY

INTS

VSB

I/O Ready. Instructs the PC87427 to extend the access cycle.

XIRQ2-0

36-35,

IINTS

VSB

X-Bus Interrupt. Converted into serial interrupt by the Interrupt

Serializer. The system conﬁguration includes the interrupt number

associated with this signal.

BIOS_SEL

O3/6

VSB

BIOS Select. BIOS image selections.

Signal

Pin(s)

I/O Buffer Type Power Well

Description

CTS1

IINTS

VDD

Clear to Send. When low, indicates that the modem or other data

transfer device is ready to exchange data.

CTS2

CTSM

107

VSB

DCD1

IINTS

VDD

Data Carrier Detected. When low, indicates that the data transfer

device, e.g., modem, has detected the data carrier.

DCD2

109

VSB

DCDM

O14/14

VSB

DSR1

IINTS

VDD

Data Set Ready. When low, indicates that the data transfer device,

e.g., modem, is ready to establish a communications link.

DSR2

DSRM

103

VSB

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