MAC7200 datasheet(813/976 Pages) FREESCALE

813 / 976 page

Initialization/Application Information

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

735

32.14.2 Application Information

Correlated output signals can be generated by all output operation modes. Bits OUDISn can be used to

control the update of these output signals.

In order to guarantee that the internal counters of correlated channels are incremented in the same clock

cycle, the internal prescalers must be set up before enabling the global prescaler. If the internal prescalers

are set after enabling the global prescaler, the internal counters may increment in the same ratio, but at a

different clock cycle.

It is recommended to drive Output Disable Input signals with the mts_flag_out signals of some UCs

running in SAIC mode. When an output disable condition happens, the software interrupt routine must

service the output channels before servicing the channels running SAIC. This procedure avoid glitches in

the output pins.

32.14.2.1 Time Base Generation

For MC, OPWFM and OPWM with internal clock source operation modes, the internal counter rate can

be modified by configuring the clock pre scaler ratio. Figure 32-57 shows an example of a time base with

pre scaler ratio equal to one. When the pre scaler is greater than one, the counter is immediately cleared

on a match and then incremented in the next pre scaled clock edge, except when running in OPWFM mode

or MC mode with internal clock source, in which case the counter will skip the next pre scaled clock edge

and continue incrementing on subsequent edges, as shown in Figure 32-58.

NOTE

MCB, OPWFMB and OPWMB modes have a different behavior

Figure 32-57. Time base period when running in the fastest pre scaler ratio

clock

pre scaled clock = 1

internal counter

match value = 3

PRE SCALED CLOCK RATIO = 1 (bypassed)

see note 1

Note 1: When a match occurs, the first clock cycle is used to

clear the internal counter, starting another period.

MAC7200 Datasheet(PDF) 813 Page - Freescale Semiconductor, Inc