Using the C30 Compiler to Interface SPI Serial EEPROMs with dsPIC33

AN1096 Using the C30 Compiler to Interface SPI Serial EEPROMs with dsPIC33F and PIC24F This application note provides assistance and source Author: Martin Kvasnicka code to ease the design process of interfacing a Microchip Technology Inc. Microchip dsPIC33F Digital Signal Controller to a Microchip SPI serial EEPROM, without the use of a hardware serial port. INTRODUCTION Figure 1 describes the hardware schematic for the interface between Microchip's 25XXX series devices The 25XXX series serial EEPROMs from Microchip ® microcontrol-and the dsPIC33F DSC or PIC24F PIC compatible and have maximumTechnology are SPI ler. The schematic shows the connections necessary clock frequencies ranging from 3 MHz to 20 MHz. Many between the DSC or PIC MCU and the serial EEPROM times when designing an application which utilizes a as tested, and the software was written assuming serial EEPROM device, it may be beneficial to use a and HOLD pins are tied tothese connections. The WP microcontroller which does not feature a dedicated VCC through resistors, because the write-protect and protocol-specific serial port. This can be due to several hold features are not used in the examples provided. possible reasons, including size restrictions or costs. In these instances, it is required of the designer to write software routines capable of generating the proper signals for communicating with the EEPROM device. FIGURE 1: CIRCUIT FOR dsPIC33F256GP710, PIC24FJ128GA010 AND 25XXX SERIES DEVICES Vcc SDA1/RG3 SCK1/INT0/RF6 SDI1/RF7100 Pin TQFP SDO1/RF8 dsPIC33FJ256GP710 U1RX/RF2 1 8 VccCS PIC24FJ128GA010 U1TX/RF3 X 2 7SO HOLDX 4 54 5 25X SS DD F F WP 3 6 SCK V V R R / / RD1 RD1 7 8 / / 0 1 Vss 4 5 SI CN1 CN1 / X TRX/ S/CN2 S/CN2 2 T U2U CT R U1 U1 Note: CS, WP and HOLD pins should all have pull-up resistors (~10k-ohms).