Operating In Capture Mode - Intel 8XC196MC User Manual

8XC196MC, MD, MH USER'S MANUAL
Each EPA channel has a control register, EPAx_CON (capture/compare channels) or
COMPx_CON (compare-only channels); an event-time register, EPAx_TIME (capture/compare
channels) or COMPx_TIME (compare-only channels); and a timer input (Figure 11-5). The con-
trol register selects the timer, the mode, and either the event to be captured or the event that is to
occur. The event-time register holds the captured timer value in capture mode and the event time
in compare mode. See "Programming the Capture/Compare Channels" on page 11-18 and "Pro-
gramming the Compare-only Channels" on page 11-22 for configuration information.
Internal clocking
with up to 6-bit prescaler
Clock on TIMER1 overflow
EPA
Interrupt
EPA x _CON
† EPA0, EPA2, and EPA4.
†† EPA1, EPA3, and EPA5
Figure 11-5. A Single EPA Capture/Compare Channel

11.4.1 Operating in Capture Mode

In capture mode, when a valid event occurs on the pin, the value of the selected timer is captured
into a buffer. The timer value is then transferred from the buffer to the EPAx_TIME register,
which sets the EPA interrupt pending bit as shown in Figure 11-6. If enabled, an interrupt is gen-
erated. If a second event occurs before the CPU reads the first timer value in EPAx_TIME, the
current timer value is loaded into the buffer and held there. After the CPU reads the EPAx_TIME
register, the contents of the capture buffer are automatically transferred into EPAx_TIME and the
EPA interrupt pending bit is set.
11-10
Timer/Counter Unit
TIMER1
TIMER2
Capture
EPA x _TIME
Buffer
Overwrite
Mode Control
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External clocking (T1CLK) with up to 6-bit prescaler
Quadrature clocking through T1CLK and T1DIR
EPA Capture/Compare
Compare
Reset Timer
Reload Waveform
Generator †
Start A/D ††
Mode Selection
Channel x
EPA Pin
TGL
A0807-01