The PD module contains eighteen (18) programmable discrete I/O channels, two programmable Synchronous/ Asynchronous communications controllers, and an ASK (amplitude shift key) transceiver.
Each discrete I/O is individually programmable, and may function as either an input or output signal. When programmed as an input, the channel may be used for either voltage measurement or switch closure sensing. Channels set for switch closure sensing can be programmed with either a 15KΩ pull-up to external VCC or a 15KΩ pull-down to ground. This feature eliminates the need for external pull-up or pull-down resistors or mechanical jumpers. When programmed as an Output, each channel can be set for High-side switch to external VCC, Low-side switch to ground, or Push/Pull operation. Each PD module includes diode clamping (useful for inductive loads, such as relays) and short circuit protection. Signal and power is isolated from the system bus. Each PD module provides a single external VCC input.
Each block contains a single channel, high-speed intelligent communications controller. Each full duplex communications controller may be individually configured for RS-232C, RS-422 or RS-485, synchronous or asynchronous operation. This controller supports automatic BREAK detection.
Both internal and system calibration are included on chip; thus, the user has the option of removing offset/gain errors internal to the A/Ds only, or removing the offset/gain errors of the complete end system.