HD64F2149 Datasheet, PDF (336/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

11.2.3 Input Capture Registers A to D (ICRA to ICRD)
Bit
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Initial value 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Read/Write R R R R R R R R R R R R R R R R
There are four input capture registers, A to D, each of which is a 16-bit read-only register.
When the rising or falling edge of the signal at an input capture input pin (FTIA to FTID) is
detected, the current FRC value is copied to the corresponding input capture register (ICRA to
ICRD). At the same time, the corresponding input capture flag (ICFA to ICFD) in TCSR is set to
1. The input capture edge is selected by the input edge select bits (IEDGA to IEDGD) in TCR.
ICRC and ICRD can be used as ICRA and ICRB buffer registers, respectively, and made to
perform buffer operations, by means of buffer enable bits A and B (BUFEA, BUFEB) in TCR.
Figure 11.2 shows the connections when ICRC is specified as the ICRA buffer register (BUFEA =
1). When ICRC is used as the ICRA buffer, both rising and falling edges can be specified as
transitions of the external input signal by setting IEDGA ≠ IEDGC. When IEDGA = IEDGC,
either the rising or falling edge is designated. See table 11.3.
Note: The FRC contents are transferred to the input capture register regardless of the value of the
input capture flag (ICF).
IEDGA BUFEA IEDGC
FTIA
Edge detect and
capture signal
generating circuit
ICRC
ICRA
FRC
Figure 11.2 Input Capture Buffering (Example)
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