Product Information

The Technobox, Inc. P/N 5283 8-Port RS232/RS422 Asynchronous Serial Communications Adapter PMC (5382) provides eight industry standard 16550-based UARTs. Four of the ports use RS232 and four use RS422 signaling levels. All eight ports are available out the PMC front-panel on J1 a 68-pin SCSI-style connector. FAST/WIDE SCSI cables can be used to connect between J1 and the user’s system wiring. All eight ports are also wired to the PN4 connector at the rear of the PMC, allowing connection to the VMEbus P2 connector for host processors supporting rear-I/O. These signals are carried on the “a” and “c” rows on the P2 connector. There are other standard connection configurations for the P0/J0 (enhanced VME and cPCI) and the “d” and “z” rows of an enhanced DIN connector.

Each port provides the full set of data and modem control lines configured for DTE (i.e., computer side) operation: RTS (Request to Send) CTS (Clear to Send) TXD (Transmit Data) RXD (Receive Data) The eight ports each provide the 4 signals above, exhausting 64 of the 68 pins on the SCSI cable; the additional 4 pins of the SCSI cable are connected to signal ground on the PMC card. For the P2 connector I/O, the signal grounds on the P2 “b” row, as established by the VMEbus specification, can be used for the RS422 port signal ground.

Since the PN4 signals and J1 signals are in parallel and are not buffered, it is not possible to use both connections simultaneously. The UARTs operate at standard baud rates from 300 baud to 115K-baud. Other odd-baud rates are possible and are available on special order. The UART IC used is a 16C554, which contains four independent 16550 UARTs. The bridge between the 16550-register set and the PCI bus is a PLX 9030 chip, this is a slave only device so all access from the host processor is done through programmed I/O to the PCI bus I/O space, as is customarily.