Interfacing Mid-Range PIC(R) MCUs with UNI/O(TM) Bus-Compatible Serial EEPROMs

AN1188 ® Interfacing Mid-Range PIC MCUs with UNI/O™ Bus-Compatible Serial EEPROMs The main features of 11XXX serial EEPROMs are: Author: Chris Parris * Single I/O pin used for communication Microchip Technology Inc. * EEPROM densities from 1 Kb to 16 Kb * Extremely small packages * Bus speed from 10 kHz up to 100 kHz INTRODUCTION * Wide voltage range from 1.8V to 5.5V As embedded systems become smaller, a growing * Low-power operation need exists to minimize I/O pin usage for communica- * Wide temperature range from -40°C to +125°C tion between devices. Microchip has addressed this * Over 1,000,000 erase/write cyclesneed by developing the UNI/O™ bus, a low-cost, easy- to-implement solution requiring only a single I/O pin for This application note is part of a series that provide bidirectional communication. source code to help the user implement the protocol with minimal effort.UNI/O bus-compatible serial EEPROMs can be used to enhance any application facing restrictions on avail- Figure 1 describes the hardware schematic for the able I/O. Such restrictions can potentially stem from interface between the Microchip 11XXX series of connectors, board space, or from the master device UNI/O bus-compatible devices and the PIC12F609 itself. microcontroller, and Figure 2 shows the schematic for the PIC16F610. The schematics show the connectionsThe 11XXX family is the newest addition to Microchip necessary between the microcontroller and the serialTechnology's broad serial EEPROM product line, and EEPROM as tested. The software was writtenis compatible with the newly developed UNI/O bus. assuming these connections. The single I/O connection between the microcontroller and the serial EEPROM includes a recommended pull-up resistor. FIGURE 1: CIRCUIT FOR PIC12F609 AND 11XXX SERIAL EEPROM (2) VCC PDIP 18VCC VSS 9 27GP5 GP0 3 C12F60 6 GP4 GP1 PI 4 5 GP3/MCLR GP2 (2) VCC