Model RDI-54 is an intelligent, 54-bit parallel digital-input-to-computer interface unit. It is packaged in a NEMA 4 enclosure for remote installation in harsh environments. There are no switches or jumpers to set to enable half-duplex operation. However, there are jumpers that can be placed to bypass the opto-isolators if you wish. Communication can be at up to 19.2 Kbaud in the isolated mode and up to 28.8 Kbaud in the non-isolated mode. (If the communication cable is short, 56 Kbaud can be realized.)
Digital Inputs may be read in 8-bit bytes at input voltages up to 50 VDC. The input lines are latched into seven 8-bit registers and outputs of the registers are multiplexed to the data bus of the microcontroller. The registers can be scanned either sequentially or at random, one byte at a time. Change-of-state flags can be set on any input bits and can be read via the serial port. This is particularly useful in applications where it is necessary to detect contact closures or openings. This change-of-state detection capability is enabled on a bit-by-bit basis.
A built-inwatchdog timer resets the pod if, for some unexpected reason, the microcontroller "hangs up" or the supply voltage drops below 4.75 VDC. Also data collected by the pod are stored in local RAM for later access through the computer's serial port. This feature facilitates a stand-alone mode of operation. For example, a portable or laptop computer that has an RS-485 port can be brought to the pod, connected, and collect the data.
