Renesas H8S/2100 Series, Hardware Manual

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Section 10 16-Bit Timer Pulse Unit (TPU)
Rev. 1.00 Apr. 28, 2008 Page 283 of 994
REJ09B0452-0100
10.5.5 Phase Counting Mode
In phase counting mode, the phase difference between two external clock inputs is detected and
TCNT is incremented/decremented accordingly. This mode can be set for channels 1 and 2. When
phase counting mode is set, an external clock is selected as the counter input clock and TCNT
operates as an up/down-counter regardless of the setting of bits TPSC2 to TPSC0 and bits CKEG1
and CKEG0 in TCR. However, the functions of bits CCLR1 and CCLR0 in TCR, and of TIOR,
TIER, and TGR are valid, and input capture/compare match and interrupt functions can be used.
This can be used for two-phase encoder pulse input. When overflow occurs while TCNT is
counting up, the TCFV flag in TSR is set; when underflow occurs while TCNT is counting down,
the TCFU flag is set. The TCFD bit in TSR is the count direction flag. Reading the TCFD flag
provides an indication of whether TCNT is counting up or down. Table 10.20 shows the
correspondence between external clock pins and channels.
Table 10.20 Phase Counting Mode Clock Input Pins
External Clock Pins
Channels A-Phase B-Phase
When channel 1 is set to phase counting mode TCLKA TCLKB
When channel 2 is set to phase counting mode TCLKC TCLKD
(1) Example of Phase Counting Mode Setting Procedure
Figure 10.25 shows an example of the phase counting mode setting procedure.
Phase counting mode
Select phase counting mode
Start count
<Phase counting mode>
Select phase counting mode with bits MD3 to
MD0 in TMDR.
Set the CST bit in TSTR to 1 to start the count
operation.
[1]
[2]
[1]
[2]
Figure 10.25 Example of Phase Counting Mode Setting Procedure