Concerto™ also supports SSI or synchronous serial interface modules similar to the Stellaris® part, and includes four independent SSIs on the host side. Each SSI is a master or slave interface for synchronous serial communication with peripheral devices that have either the Freescale SPI, micro wire, or Texas Instruments synchronous serial interfaces. The SSI module features a programmable clock bit-rate and a pre-scaler, and SPI will support SPI communications up to 25 Mbps in both transmit and receive mode. The data frame size is programmable from four to six bits wide, and transmit and receive FIFOs are independent in eight words deep by 16-bits wide. Efficient data transfer with SSI can be ensured through the µDMA with single and through-burst capabilities. The Concerto SSI also supports an internal loopback test mode for diagnostics and debugging.