PC87373 datasheet(149/174 Pages) NSC

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12.0 Legacy Functional Blocks (Continued)

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Revision 1.1

12.4 KEYBOARD AND MOUSE CONTROLLER (KBC)

12.4.1 General Description

The KBC is implemented physically as a single hardware module and houses two separate logical devices: a mouse con-

troller (Logical Device 5) and a keyboard controller (Logical Device 6). The KBC is functionally equivalent to the industry

standard 8042AH keyboard controller. The 8042AH datasheet can be used as a detailed technical reference for the KBC.

The hardware KBC module is integrated to provide the following pin functions: KBRST (P20), GA20 (P21), KBDAT, KBCLK,

MDAT and MCLK. KBRST and GA20 are implemented as bi-directional open-drain pins with internal active pull-up. The key-

board and mouse interfaces are implemented as bi-directional open-drain pins. Their internal connections are shown in

Figure 43.

Ports P10-P17 and P22-P27 of the KBC core are not available on dedicated pins; neither are T0 and T1. P10, P11, P22,

P23, P26, P27, T0 and T1 are used to implement the keyboard and mouse interface.

The KBC executes a program fetched from an on-chip 2 Kbyte ROM. The code programed in this ROM is user-customizable.

The KBC has two interrupt request signals: one for the keyboard and one for the mouse. The interrupt requests are imple-

mented using ports P24 and P25 of the KBC core. The interrupt requests are controlled exclusively by the KBC firmware,

except for the IRQ type and number, which are set by configuration registers (see Section 3.2.3 on page 36).

The interrupt requests are implemented as bi-directional signals. When an I/O port is read, all unused bits return the value

latched in the output registers of the ports.

For KBC firmware that implements interrupt-on-OBF schemes, the following is the recommended implementation:

1. Put the data in DBBOUT.

2. Set the appropriate port bit to issue an interrupt request.

Figure 43. Keyboard and Mouse Interfaces

KBD IRQ

Mouse IRQ

KBC

KBCLK

KBDAT

P10

MCLK

MDAT

P11

P26

P27

P23

P22

STATUS

DBBIN

DBBOUT

Matrix

P24

P25

P20

P21

P12

KBRST

GA20

P12

P17

P16

PC87373

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