Sharp Blue Treak LH75400 User Manual

6/17/03 18-1Chapter 18Synchronous Serial PortThe Synchronous Serial Port (SSP) is a master-only interface for synchronous serialcommunication with slave peripheral devices that have Motorola SPI, National Semicon-ductor Microwire, or Texas Instruments DSP-compatible synchronous serial interfaces.Figure 18-1 shows a block diagram of the SSP.18.1 SSP FeaturesThe SSP block provides the following features.• Synchronous Serial Interface in Master Only Mode. The SSP performs serial communi-cations as a master device in one of three modes:– Motorola SPI– Texas Instruments DSP-compatible synchronous serial interface– National Semiconductor Microwire• Two 16-bit-wide, 8-entry-deep FIFOs, one for transmitting data and one for receiving data:– The transmit FIFO takes data written to it and transmits it on the serial interface.– The receive FIFO parallellizes the serial data stream and presents it in a FIFO foraccess by other devices.• If the receive FIFO is not empty, the SSP can assert an interrupt after a specified numberof clock ticks elapses following the start of a receive transfer. This feature permitsinterrupt-driven data transfers that are greater than the FIFO watermark, but not an evenmultiple of it.• Programmable clock bit rate.• Programmable data frame size, from 4 to 16 bits long, depending on the size of data pro-grammed. Each frame transmits starting with the most-significant bit.• Four interrupts, each of which can be individually enabled or disabled using the SSPControl Register bits. A combined interrupt is also generated as an OR function of theindividual interrupt requests.• Loopback Test Mode.