MAC7200 datasheet(804/976 Pages) FREESCALE

804 / 976 page

Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

726

Freescale Semiconductor

The FLAG bit is not set either in case of a FORCMA or FORCMB or even if both forces are issued at the

same time.

NOTE

FORCMA and FORCMB have the same behavior even in Freeze or normal

mode regarding the output pin transition.

When FORCMA is issued along with FORCMB the output flip-flop is set to the opposite of EDPOL bit

value. This is equivalent of saying that.FORCMA has precedence over FORCMB when lead dead time

insertion is selected and FORCMB has precedence over FORCMA when trail dead time insertion is

selected.

Duty cycle from 0% to 100% can be generated by setting appropriate values to A1 and B1 registers

relatively to the period of the external time base. Setting A1=1 generates a 100% duty cycle waveform. If

A1 > maximum value of the selected counter bus period, then a 0% duty cycle is produced. Assuming

EDPOL is set to one and OPWMCB mode with trail dead time insertion, 100% duty cycle signals can be

generated if B1 occurs at or after the cycle boundary (external counter = 1).

NOTE

A special case occurs when A1 is set to (external counter bus period)/2,

which is the maximum value of the external counter. In this case the output

flip-flop is constantly set to the EDPOL bit value.

The internal channel logic prevents matches from one cycle to propagate to the next cycle. In trail dead

time insertion B1 match from cycle (n) could eventually cross the cycle boundary and occur in cycle (n+1).

In this case B1 match is masked out and does not cause the output flip-flop to transition. Therefore matches

in cycle(n+1) are not affected by the late B1 matches from cycle(n).

Figure 32-48 shows a 100% duty cycle output signal generated by setting A1=4 and B1=3. In this case the

trailing edge is positioned at the boundary of cycle n+1, which is actually considered to belong to cycle

n+2 and therefore does not cause the output flip-flip to transition.

MAC7200 Datasheet(PDF) 804 Page - Freescale Semiconductor, Inc