Technical data

USB and PS/2 Multimedia Keyboard Interface, Rev. 1
Freescale Semiconductor 7
Chapter 1
USB and PS/2 Multimedia Keyboard Interface
1.1 Introduction
This manual describes a reference design of a Universal Serial Bus and PS/2 multimedia keyboard
interface for Microsoft Windows by using the MC68HC908JB8.
For the full MC68HC908JB8 specification, please refer to the data sheet, Freescale order number:
MC68HC908JB8/D.
1.2 Overview
The Freescale MC68HC908JB8 is a member of the HC08 Family of microcontrollers (MCUs). The
features of the MC68HC908JB8 include a configured Universal Serial Bus (USB) or PS/2 interface, which
makes this MCU suited for personal computer Human Interface Devices (HID), such as mice and
keyboards. The MC68HC908JB8 is available in several packages to fit into various applications. A
multimedia keyboard with USB and PS/2 interface is demonstrated using the MC68HC908JB8 with a
44-pin QFP package. The main features of the keyboard include:
• Fully USB specification 1.1 compliant
• USB or PS/2 interface auto detect
• Windows 98, ME and 2000 compatible
• Power management keys (power, wake and sleep) support
• Multimedia key support
• In-circuit programming for firmware modification
1.3 44-pin QFP MC68HC908JB8 Features
The 44-pin QFP MC68HC908JB8 is targeted for USB and PS/2 interface keyboard applications with
minimum external components needed. Features include:
• USB D+ and D– pins shared with PS/2 data and clock pins
• 27 out of 37 I/O pins with internal pull-up supports up to 8 x 19 key matrix
• 10mA direct drive pins for the Num Lock, Caps Lock and Scroll Lock LEDs
• Internal 1.5K pull-up for USB D– data line
• Internal 5K pull-ups for PS/2 data and clock pins