Reset-Synchronized Pwm Mode - Hitachi SH7032 Hardware Manual

10.4.5

Reset-Synchronized PWM Mode

In reset-synchronized PWM mode, three pairs of complementary positive and negative PWM
waveforms that share a common wave turning point can be obtained using channels 3 and 4. When
set for reset-synchronized PWM mode, the TIOCA3, TIOCB3, TIOCA4, TOCXA4, TIOCB4, and
TOCXB4 pins become PWM output pins and TCNT3 becomes an up-counter. Table 10.12 shows
the PWM output pins used and table 10.13 shows the settings of the registers used.
Table 10.12 Output Pins for Reset-Synchronized PWM Mode
Channel Output Pin
3 TIOCA3
TIOCB3
4 TIOCA4
TOCXA4
TIOCB4
TOCXB4
Table 10.13 Register Settings for Reset-Synchronized PWM Mode
Register Setting
TCNT3 Initial setting of H'0000
TCNT4 Not used (functions independently)
GRA3 Sets count cycle for TCNT3
GRB3 Sets the turning point for PWM waveform output by the TIOCA3 and TIOCB3 pins
GRA4 Sets the turning point for PWM waveform output by the TIOCA4 and TOCXA4 pins
GRB4 Sets the turning point for PWM waveform output by the TIOCB4 and TOCXB4 pins
Procedure for Selecting Reset-Synchronized PWM Mode (figure 10.31):
1. Clear the STR3 bit in TSTR to halt TCNT3. Reset-synchronized PWM mode must be set while
TCNT3 is halted.
2. Set bits TPSC2-TPSC0 in TCR to select the counter clock source for channel 3. If an external
clock source is selected, select the external clock edge with bits CKEG1 and CKEG0 in TCR.
3. Set bits CCLR1 and CCLR0 in TCR3 to select GRA3 as a counter clear source.
4. Set bits CMD1 and CMD0 in TFCR to select reset-synchronized PWM mode. TIOCA3,
TIOCB3, TIOCA4, TIOCB4, TOCXA4, and TOCXB4 become PWM output pins.
5. Reset TCNT3 (to H'0000). TCNT4 need not be set.
268
Description
PWM output 1
PWM output 1' (negative-phase waveform of PWM output 1)
PWM output 2
PWM output 2' (negative-phase waveform of PWM output 2)
PWM output 3
PWM output 3' (negative-phase waveform of PWM output 3)