5.3 Serial Communication on MVIO Pins

Another use case of the MVIO module is the ability to configure any of the available serial communication peripherals on a device to operate on the V_DDIOx voltage domain rather than the V_DD domain as they normally would. This means that when serial communication peripherals are configured to operate on MVIO specific pins, the logic levels on those pins will be scaled to match the respective V_DDIOx supply voltage. A simple example of this would be an application where a PIC or AVR microcontroller operates at a V_DD of 5V where it must measure data from a sensor that also operates at 5V, and then transmit it using I²C to another main microcontroller or high end microprocessor that operates at 1.8V. This can be accomplished on a device with MVIO by supplying 5V to the V_DD pin and 1.8V to the V_DDIOx pin of the microcontroller. The device can then interface the 5V sensor using pins on the V_DD domain in this example, and an I²C module can be configured to operate on MVIO pins that are on the V_DDIOx voltage domain. The figure below illustrates this example implemented on the PIC18-Q24 device family and shows waveforms of serial communication happening on the same device in two different voltage domains. Although the example below is shown on the PIC18-Q24, the same principle of operation applies to all PIC and AVR devices that have MVIO.