IP-Octal Serial is part of the Industry Pack family of modular I/O components. It is based around the Signetics CMOS SCC2698 Octal Universal Asynchronous Receiver/Transmitter. This component provides eight channels of full-duplex asynchronous serial communications, baud rate generators, state change detect logic, and four 16-bit counter/timers.
A block diagram of the IP-Octal Serial is shown below in Figure 1.
RS-232-C communication levels are provided by CMOS MC14C88 and MC14C89 transmitters and receivers. Five signals for each channel on the RS-232-C interface are supported: Transmit Data (TxD), Receive Data (RxD), Ready-To-Send (RTS), Clear-To-Send (CTS) and ground. The MC14C89 Receivers are biased at 1.5 volts nominally to permit a variety of input signal levels to be received without additional interface circuitry. The interface circuit is shown below in Figure 2. Protection diodes are provided in the +/-12 volt supply lines to permit connection to powered equipment, even if the IndustryPack is unpowered.
Vectored interrupts are fully supported. A common 8-bit vector register is provided. Channels a,b,c,d interrupt on IRQ0. Channels e,f,g,h interrupt on IRQ1.
DMA is supported on channels c and d. If DMA is used, then the Request-To-Send lines on these two channels are not available.
The IndustryPack is contolled y a single CMOS 22V10 type PAL.
Connection to the IP-Octal Serial is via a standard 50-conductor ribbon cable. An optional connection panel is available which provides a 50-pin flat cable input with 16 DB-9 male or female connectors. The metal reinforced connection panel mounts in a standard 19 inch rack-mount space.
If compatibility with pre-1994 IP-Octal Serial IndustryPacks is required or for RS232D environments requiring a higher level of noise immunity, a special order option, Option-01, is available which shifts the nominal threshold slightly less than one volt. This option does not provide TTL switching thresholds.
Reprints of the Data Sheets for the SCC2698B, Schematic and PAL equations, and sample serial cables are available as part of the IP-Octal Serial Engineering Kit. This Kit is recommended for first time users of the IP-Octal Serial.