Digital I/O and Counter/Timer

The XR17D158 UART offers 8 built-in digital I/O lines and a programmable counter/timer. The 8 DIO lines and the counter/timer signals are brought out to an 8-pin connector on the lower edge of the board.

The DIO and counter/timer signals are 3.3V nominal logic signals and have ESD protection.

The 8 DIO lines are also available on the 8 extra pins on the two serial I/O connectors to provide compatibility with EMM-8P. The user must be made aware of the limitation that only one source can be used for input, either the serial port connector or the dedicated DIO connector.

The counter/timer’s output is multiplexed under software control to DIO 0. The counter/timer’s input is programmable for either an internal clock or an external signal. The external signal is available on a pin on the digital I/O connector.

DIO 0 has an LED connected to it for use in displaying board activity or health status.