Mobile I/O Devices Unburden Host Processor

Promising to ease handheld-device designs, the LM8322 and LM8333 mobile I/O chips offer flexible configurations, modular integration, and provide a migration path across multiple products, thereby minimizing costs and development time. Enabling the use of the same host processor and companion across multiple product versions, the off-the-shelf devices integrate embedded key-scan functions, I/O expansion, and LED control capabilities. Communication from the chips is via a standard I2C bus and interrupt signal that requires three pins. A set of commands and scripts for PWM-signal generation allows the host to configure the mobile I/O device's resources or trigger command execution. The LM8322 supports keypad matrices up to 104 keys while the LM8333 supports up to 72 keys. Both have eight special-function keys that take priority in the key rolling sequence. The LM8322 is available in a 36-pin micro array package and the LM8333 comes in both 32-pin LLP and 49-pin micro array packages. Prices are $2.65, $1.95, and $2.05 each/1,000, respectively. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959.