Using C and a Timer to Interface 8051 MCUs with UNI/O(TM) Bus-Compatible Serial EEPROMs

AN1185 Using C and a Timer to Interface 8051 MCUs with UNI/O™ Bus-Compatible Serial EEPROMs Some of the main features of 11XXX serial EEPROMs Author: Alexandru Valeanu are: Microchip Technology Inc. * Single I/O pin used for communication * EEPROM densities from 1 Kbits to 16 Kbits * Extremely small packagesINTRODUCTION * Bus speed from 10 kHz up to 100 kHz As embedded systems become smaller, a growing * Voltage range from 1.8V to 5.5V need exists to minimize I/O pin usage for communica- * Low-power operation tion between devices. Microchip has addressed this need by developing the UNI/O™ bus, a low-cost, easy- * Temperature range from -40°C to +125°C to-implement solution requiring only a single I/O pin for * Over 1,000,000 erase/write cycles bidirectional communication. This application note is part of a series that provide UNI/O bus-compatible serial EEPROMs can be used to source code to help the user implement the protocol enhance any application facing restrictions on avail- with minimal effort. able I/O. Such restrictions can potentially stem from Figure 1 is the hardware schematic depicting the inter- connectors, board space or from the microcontroller face between the Microchip 11XXX series of UNI/O itself. bus-compatible serial EEPROMs and NXP's The 11XXX family is the newest addition to Microchip P89LPC952 8051-based MCU. The schematic shows Technology's broad serial EEPROM product line, and the connections necessary between the MCU and the is compatible with the newly developed UNI/O bus. serial EEPROM as tested. The software was written assuming these connections. The single I/O connec- tion between the MCU and the serial EEPROM includes a recommended pull-up resistor. A decoupling CC and VSS is also recommended.capacitor across V FIGURE 1: CIRCUIT FOR P89LPC952 MCU AND 11XXX SERIAL EEPROM (1) VCC 11XXX 2 VCC (2) 3SS 10 k?V 7P1.3 INT0/SDA1 SCIO P89LPC952