Holtek Semiconductor Inc HT6542B Datasheet
Keyboard Controller with PS/2
Features
•
High reliability MOS technology
•
8042-type host interface
•
6MHz-12MHz operating frequency
•
Communicates with keyboard directly
•
Provides enhanced Gate A20 switching
General Description
The HT6542B is a keyboard controller developed by Holtek with a 4-bit microprocessor . It is
pin-to-pin compatible with Intel 8042 keyboard
controller used in IBM PC’s. PC manufacturers
need not modify any printed wiring layout
when using the HT6542B in lieu of the Intel
Pin Assignment
40 Pin DIP package 44 Pin PLCC package
•
Support PS/2 compatible mouse
•
Auto-detect AT and PS/2 motherboard
•
Support 40 pin DIP and 44 pin PLCC packages
8042 based keyboard controller. Furthermore,
the HT6542B can support a system clock speed
of up to 12MHz. The HT6542B can detect th e
motherboard type automatically, therefore it
can be employed on both of AT and PS/2 motherboard.
HT6542B
1 30th Nov ’95
Block Diagram
HT6542B
Pin Description
Pin No.
(DIP)
1 2 KBCI I Keyboard clock input pin
2,3 3,4 OSCI,OSCO I
45
5,7,11,25
67
89
910 A0 I
Pin No.
(PLCC)
1,6,8,12,13,
23,29,34
Pin
Name
RES I
NC — No connection
CS I Host-interface chip select, active low
RD I Host-interface read signal, active low
I/O Pin Descriptions
System clock input pin, to generate internal
oscillator signal
Low level to reset HT6542B. After
level HT6542B needs 10ms to initial internal circuit
Host-interface address select input. When high, it
selects the command/sta tus registers; when low it
selects the data register
2 30th Nov ’95
RES goes to high
HT6542B
Pin No.
(DIP)
10 11 WR I Host-interface write signal, active low
12~19 14~21 D0~D7 I/O
20 22 VSS — Circuit ground
21 24 RC O Host-reset control signal output
22 25 A20 O Gate A20 control signal output
23 26 P22/MSDO I/O
24 27 P23/MSCO I/O
26 28 TEST I
27 30 P10/KBDI I/O
28 31 P11/MSDI I/O
29~33
34 38
35 39 KB-OBFO O
36 40 MS-OBFO O
37 41 KBCO O
38 42 KBDO O
39 43 KBDI/MSCI I
40 44 VDD — Positive power supply
Pin No.
(PLCC)
32~33
35~37
Pin
Name
P12~P16 I/O General purpose input/output pins
KBD-INH I
I/O Pin Descriptions
Host interface data bus. An 8-bit bi-directional port
for data transfers between the host CPU and the
HT6542B
General purpose input/output pin for AT
motherboard.
Mouse data output pin for PS/2 motherboard
General purpose input/output pin for AT
motherboard.
Mouse clock output pin for PS/2 motherboard
Test input pin, for IC test only. Connected to VCC in
applications
General purpose input/output pin for AT
motherboard.
Keyboard data input pin for PS/2 motherboard
General purpose input/output pin for AT
motherboard.
Mouse data input pin for PS/2 motherboard
Keyboard inhibit input. When low, keyboard is
inhibited. When high, keyboard transmission is
enabled.
Keyboard output buffer full interrupt for AT and
PS/2 mother board (active high)
Output low for AT mothboard.
Mouse output b uffer full interrup t for PS/2 mo ther
board (active high).
Keyboard clock output pin for AT and PS/2
motherboard.
Keyboard data output pin for AT and PS/2
motherboard.
Keyboard data input pin for AT motherboard
Mouse clock input pin for PS/2 motherboard
Absolu te Maximu m R a tin g s
Supply Voltage ............................ –0.3V to 5.5V
Input Voltage .................. V
–0.3V to VDD+0.3
SS
Storage T emperature ............... –50
Operating Temperature ................. 0
3 30th Nov ’95
°C to 125°C
°C to 70°C
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