PC87413 datasheet(229/257 Pages) NSC

229 / 257 page

10.0 Legacy Functional Blocks (Continued)

Revision 1.2

229

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10.4 KEYBOARD AND MOUSE CONTROLLER (KBC)

10.4.1

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

The hardware KBC module is integrated to provide the following pin functions: P12, P16, P17, KBRST (P20), GA20 (P21),

KBDAT, KBCLK, MDAT and MCLK. KBRST and GA20 are implemented as bidirectional open-drain pins. The keyboard and

mouse interfaces are implemented as bidirectional open-drain pins. P12, P16 and P17 are implemented as quasi-bidirec-

tional pins. Their internal connections are shown in Figure 53.

P10, P11, P13-P15 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.

Internal pull-ups are implemented only on P12, P16 and P17.

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

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

implemented using ports P24 and P25 of the KBC core. The interrupt requests are controlled exclusively by the KBC firm-

ware, except for the type and number, which are affected by configuration registers (see Section 3.2.3 on page 40).

The interrupt requests are implemented as bidirectional 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 53. 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

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