PC87317 datasheet(48/272 Pages) NSC

48 / 272 page

Keyboard (and Mouse) Controller (KBC) (Logical Devices 0 and 1)

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FIGURE 3-2. System Interfaces

3.2

FUNCTIONAL OVERVIEW

The KBC supports two external devices — a keyboard and

a mouse. Each device communicates with the KBC via two

bidirectional serial signals. Five additional external general-

purpose I/O signals are provided.

KBC operation involves three signal interfaces:

External I/O interface

Internal KBC - PC87317VUL interface

PC87317VUL - PC chip set interface.

These system interfaces are shown in FIGURE 3-2 "Sys-

tem Interfaces".

The KBC uses two data registers (for input and output) and

a status register to communicate with the PC87317VUL

central system. Data exchange between these units may be

based on programmed I/O or interrupt-driven.

The KBC has two internal interrupts: the Input Buffer Full

(IBF) interrupt and Timer Overflow interrupt (see FIGURE

3-1 "KBC System Functional Block Diagram" on page 47).

These two interrupts can be independently enabled or dis-

abled by KBC firmware. Both are disabled by a hard reset.

These two interrupts only affect the execution flow of the

KBC firmware, and have no connection with the external in-

terrupts requested by this logical device.

The KBC can generate two external interrupt requests.

These request signals are controlled by the KBC firmware

which generates them by manipulating I/O port signals. See

Section 3.3.2 "Interrupt Request Signals".

The PC87317VUL supports the KBC and handles interac-

tions with the PC chip set. In addition to data transfer, these

interactions include KBC configuration, activation and sta-

tus monitoring. The PC87317VUL interconnects with the

host via one interface that is shared by all chip devices.

The KBC clock is generated from the main clock of the chip,

which may come from an external clock source or from the

internal frequency multiplier. (See Section 3.3 "DEVICE

CONFIGURATION" and FIGURE 3-5 "Timing Generation

and Timer Circuit" on page 50.) The KBC clock rate is con-

figured by the SIO Configuration Registers.

3.3

DEVICE CONFIGURATION

The KBC hardware contains two logical devices—the KBC

(logical device 0) and the mouse (logical device 1).

3.3.1

I/O Address Space

The KBC has two I/O addresses and one IRQ line (KBC

IRQ) and can operate without the companion mouse.

The mouse cannot operate without the KBC device. It has

one IRQ line (mouse IRQ) but has no I/O address. It utilizes

the KBC I/O addresses.

3.3.2

Interrupt Request Signals

The KBC IRQ and Mouse IRQ interrupt request signals are

identical to (or functions of) the P24 and P25 signals of the

8042. These interrupt request signals are routed internally

to the Plug and Play interrupt Matrix and may be routed to

user-programmable IRQ pins. Each logical device is inde-

pendently controlled.

The Interrupt Select registers (index 70h for each logical de-

vice) select the IRQ pin to which the corresponding interrupt

request is routed. The interrupt may also be disabled by not

routing its request signal to any IRQ pin.

Bit 0 of the Interrupt Type registers (index 71h for each log-

ical device) determines whether the interrupts are passed

(bit 0 = 0) or latched (bit 0 = 1). If bit 0 = 0, interrupt request

signals (P24 and P25) are passed directly to the selected

IRQ pin. If bit 0 = 1, interrupt request signals that become

Chip Set

SA15-0

PC87317VUL

XD7-0

A15-0

D7-0

AEN

KBC IRQ

Mouse IRQ

KBC Device

KBCLK

KBDAT

TEST0

P10

Keyboard Clock

Keyboard Data

MCLK

MDAT

TEST1

P11

Mouse Clock

Mouse Data

P26

P27

P23

P22

STATUS

DBBIN

DBBOUT

Plug and

Play

Matrix

P24

P25

P16

P17

P20

P21

P12

IRQn

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