CHAPTER 11

EVENT PROCESSOR ARRAY (EPA)

Control applications often require high-speed event control. For example, the controller may need to periodically generate pulse-width modulated outputs or an interrupt. In another application, the controller may monitor an input signal to determine the status of an external device. The event processor array (EPA) was designed to reduce the CPU overhead associated with these types of event control. This chapter describes the EPA and its timers and explains how to configure and program them.

11.1 EPA FUNCTIONAL OVERVIEW

The EPA performs input and output functions associated with two timer/counters, timer 1 and timer 2 (Figure 11-1). In the input mode, the EPA monitors an input pin for an event: a rising edge, a falling edge, or an edge in either direction. When the event occurs, the EPA records the value of the timer/counter, so that the event is tagged with a time. This is called an input capture. Input captures are buffered to allow two captures before an overrun occurs.

In the output mode, the EPA monitors a timer/counter and compares its value with a value stored in a register. When the timer/counter value matches the stored value, the EPA can trigger an event: a timer reset, an A/D conversion, a waveform generator reload, or an output event (set a pin, clear a pin, toggle a pin, or take no action). This is called an output compare.

Each input capture or an output compare sets an interrupt pending bit. This bit can optionally cause an interrupt. Table 11-1 lists the capture/compare and compare-only channels for each de- vice in the 8XC196Mx family.

Table 11-1. EPA Channels

Device

Capture/Compare Channels

Compare-only Channels

 

 

 

8XC196MC

EPA3:0

COMP3:0

8XC196MD

EPA5:0

COMP5:0

8XC196MH

EPA1:0

COMP3:0

11-1

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Intel 8XC196MD manual EPA Functional Overview, EPA Channels, Device Capture/Compare Channels Compare-only Channels, COMP30