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 8042 based keyboard controller. Furthermore, the HT6542B can support a system clock speed of up to 12MHz. The HT6542B can detect the motherboard type automatically, therefore it can be employed on both of AT and PS/2 motherboard.

Features
• High reliability MOS technology
• 8042-type host interface
• 6MHz-12MHz operating frequency
• Communicates with keyboard directly
• Provides enhanced Gate A20 switching
• Support PS/2 compatible mouse
• Auto-detect AT and PS/2 motherboard
• Support 40 pin DIP and 44 pin PLCC packages