22.4 Input Capture Mode
Input Capture mode is used to capture a timer value from an independent timer base, upon an event, on an input pin or other internal trigger source. The input capture features are useful in applications requiring frequency (time period) and pulse measurement. Figure 22-4 depicts a simplified block diagram of Input Capture mode.
Input Capture mode uses a dedicated 16/32-bit, synchronous, up counting timer for the capture function. The timer value is written to the FIFO when a capture event occurs. The internal value may be read (with a synchronization delay) using the CCPxTMRH/L registers.
To use Input Capture mode, the CCSEL bit (CCPxCON1L[4]) must be set. The T32 and the MOD[3:0] bits are used to select the proper Capture mode, as shown in Table 22-3.
| MOD[3:0] (CCPxCON1L[3:0]) | T32 (CCPxCON1L[5]) | Operating Mode |
|---|---|---|
0000 | 0 | Edge Detect (16-bit capture) |
0000 | 1 | Edge Detect (32-bit capture) |
0001 | 0 | Every Rising (16-bit capture) |
0001 | 1 | Every Rising (32-bit capture) |
0010 | 0 | Every Falling (16-bit capture) |
0010 | 1 | Every Falling (32-bit capture) |
0011 | 0 | Every Rising/Falling (16-bit capture) |
0011 | 1 | Every Rising/Falling (32-bit capture) |
0100 | 0 | Every 4th Rising (16-bit capture) |
0100 | 1 | Every 4th Rising (32-bit capture) |
0101 | 0 | Every 16th Rising (16-bit capture) |
0101 | 1 | Every 16th Rising (32-bit capture) |