An EXAR XR16C854 implements the UART interface. This quad UART device is compatible with the industry standard 16550 UART, but is equipped with 128 byte FIFOs, independent Tx and Rx FIFO counters, automatic hardware/software flow control, and many other enhanced features. An 18.432 MHz oscillator supplies the reference clock for this device allowing baud rates up to 1.152 Mbps.
The synchronous interface uses a Zilog Serial Communication Controller, the Z85C30. This dual channel, multi-protocol device can implement various bit-oriented and byte-oriented synchronous protocols such as HDLC and IBM Bisync and handles asynchronous formats as well.
The PMC-4U also has a wide range of IO drivers and receivers to interface with these two devices. There are 16 differential RS422/485 transceivers that can be configured as either receivers or transmitters, eight single-ended RS188/232/423 drivers operating at selectable voltage levels, and eight single-ended receivers capable of up to +/- 25V input range. There are also two enhanced hysteresis (~1.5V) RS423 receivers for handling noisy input signals and two open drain outputs that sink up to 65 mA. The differential input signals are selectively terminated with switched 150Ω terminations. All IO lines have series 33Ω resistors for circuit protection.
The UART, SCC, and IO lines all interface through the Xilinx FPGA to allow maximum flexibility of connections. All configuration registers internal to the Xilinx support read and write operations for software convenience. All addresses are long word aligned including the UART and SCC internal registers even though they have only a byte-wide data interface. Please see the XR16C854 and Z85C30 data sheets and user’s manuals for more information on register access and functions.
The PMC-4U conforms to the PMC and CMC draft standards. This guarantees compatibility with multiple PMC Carrier boards. Because the PMC may be mounted on different form factors, while maintaining plug and software compatibility, system prototyping may be done on one PMC Carrier board, with final system implementation on a different one.
PMC-4U uses a 10 mm inter-board spacing for the front panel, standoffs, and PMC connectors. The 10 mm height is the "standard" height and will work in most systems with most carriers. If your carrier has non-standard connectors [height] to mate with the PMC-4U, please let us know. We may be able to do a special build with a different height connector to compensate.
Interrupts are supported by the PMC-4U. Each of the four UARTs and the SCC has a maskable input to the interrupt generation logic in the Xilinx.
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