11.4.11 I/O integrity Module (IOIM)
The purpose of the I/O Integrity Monitor module is to provide safety components for the dsPIC33A family of devices. To keep up with the safety demand, IOIM is used to monitor the connectivity of a selected reference signal against a feedback signal with user configurable path delay.
Typical uses include:
- To increase protection for customers who are building safety sensitive applications
- To simplify structural tests for safety applications
- To ensure the pin has been connected correctly in its final environment by using structural tests
The I/O Integrity Monitor is a change detector circuit that compares a reference signal with a selected feedback signal. The module detects a change in the reference signal to start the blanking timer, and the blanking timer is used to account for the feedback path delay. After a programmable amount of time, the state of the selected feedback input is compared with the state of the reference input.
If a mismatch is sampled at any time or a configured time after the blanking period, then an error event is generated. The module gives an error event interrupt on a mismatch event.
Every error event is used to increment the user-defined Error Counter value; the module gives an overflow status bit once the Error Counter reaches the overflow state.
A typical application for the I/O Integrity Monitor is to compare the data supplied to an output pin with the data read from the output pin driver. The output pin driver data is supplied to the monitor via an input buffer. If desired, a second pin can be used to monitor the output pin data at a remote location, somewhere on the PCB or far from the chip.
The I/O Integrity Monitor is typically used to monitor the integrity of a signal generated by the MCU. However, it can also be used to monitor any signal generated outside of the MCU by connecting the reference input and feedback inputs to the appropriate external monitoring points.