SH7041A datasheet(396/923 Pages) RENESAS

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• Register operation

In complementary PWM mode, nine registers are used, comprising compare registers, buffer

registers, and temporary registers. Figure 12.40 shows an example of complementary PWM

mode operation.

The registers which are constantly compared with the counters to perform PWM output are

TGR3B, TGR4A, and TGR4B. When these registers match the counter, the value set in bits

OLSN and OLSP in the timer output control register (TOCR) is output.

The buffer registers for these compare registers are TGR3D, TGR4C, and TGR4D.

Between a buffer register and compare register there is a temporary register. The temporary

registers cannot be accessed by the CPU.

Data in a compare register is changed by writing the new data to the corresponding buffer

The data written to a buffer register is constantly transferred to the temporary register in the Ta

interval. Data is not transferred to the temporary register in the Tb interval. Data written to a

buffer register in this interval is transferred to the temporary register at the end of the Tb

interval.

The value transferred to a temporary register is transferred to the compare register when

TCNTS for which the Tb interval ends matches TGR3A when counting up, or H'0000 when

counting down. The timing for transfer from the temporary register to the compare register can

be selected with bits MD3–MD0 in the timer mode register (TMDR). Figure 12.40 shows an

example in which the mode is selected in which the change is made in the trough.

In the tb interval (tb2 in figure 12.40) in which data transfer to the temporary register is not

performed, the temporary register has the same function as the compare register, and is

compared with the counter. In this interval, therefore, there are two compare registers for one-

phase output, with the compare register containing the pre-change data, and the temporary

TCNTS—and two registers—compare register and temporary register—are compared, and

PWM output controlled accordingly.

SH7041A Datasheet(PDF) 396 Page - Renesas Technology Corp