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THROUGH THE LOOKING GLASS

Taking a Look at the PIC18Cxxx Series
by David Brobst

Start ý PIC18Cxxx Chips ý Memory ý Data Memory ý Advanced Indirect Addressing ý Deep and Accessible Stack ý Interrupts ý Power-On Features ý Clock Speed ý 10-Bit A/D ý Hardware Multiplier ý Timers ý CCP/PWM ý USART ý I²C Master ý Table Read/Write ý Current Status ý Sources and PDF

I²C MASTER

Almost from the beginning, controllers supported slave mode I²C communication. However, this was of limited use because most embedded systems have a single controller that acts as a master and talks to I²C peripherals such as EEPROM, real-time clocks, and A/Ds. So, the hardware I²C port sat dormant on many a mid-range PIC device while the controller used I²C devices and communicated to them with a bit-banged firmware solution. Fortunately, the new PIC18Cxxx series rectifies this gaffe and provides a hardware I²C master solution.

The new I²C peripheral fully supports all master modes of the Philips I²C specification in the form of Master Synchronous Serial Port (MSSP). Multi-master mode, 7- and 10-bit addressing, clock arbitration, and 400-kHz mode are supported by the new MSSP. I²C is an involved communication protocol, and it is easy to lose the forest through the trees. However, it is possible to fully realize the benefits of the I²C port on the PIC18Cxxx. Listing 2 gives some sample code that shows how easy it is to implement I²C communication. Note that the code is basic and does not test for all of the various error conditions.

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