Enhanced Modular Input/Output Subsystem (eMIOS)MPC5566 Microcontroller Reference Manual, Rev. 2Freescale Semiconductor 17-7117.4.4.4.18 Output Pulse-Width Modulation, Buffered Mode (OPWMB)The following table lists the output pulse-width modulation buffered mode settings:OPWMB mode is used to generate pulses with programmable leading and trailing edge placement. Anexternal counter is selected from one of the counter buses. The A1 register value defines the first edge andB1 defines the second edge. The output signal polarity is defined by the EDPOL bit. If EDPOL is zero, anegative edge occurs when A1 matches the selected counter bus and a positive edge occurs when B1matches the selected counter bus.The A1 and B1 registers are double buffered and updated from A2 and B2, respectively, at the cycleboundary. The load operation is similar to the OPWFMB mode.Refer to Figure 17-46 for more information on A1 and B1 register updates.Flags are generated at B1 matches when MODE[5] is cleared, or on both A1 and B1 matches whenMODE[5] is set. If subsequent matches occur on comparators A and B, the PWM pulses continue to begenerated regardless of the state of the FLAG bit.The FORCMA and FORCMB bits allow software to force the output flip-flop to the level correspondingto a match on A1 or B1 respectively. FLAG is not set by the FORCMA and FORCMB operations.The following rules apply to the OPWMB mode:• B1 matches have precedence over A1 matches if they occur at the same time within the samecounter cycle.• A1 = 0 match from cycle (n) has precedence over a B1 match from cycle (n-1).• A1 matches are masked if they occur after a B1 match within the same cycle.• Values written to A2 or B2 on cycle (n) are loaded to A1 or B1 at the following cycle boundary(assuming EMIOS_OUDR[n] is not asserted). Thus the new values are used for A1 and B1matches in cycle (n+1).Table 17-31. OPWMB Operating ModesMODE[0:6] Unified Channel OPWMB Operating Mode0b1100000 Output pulse-width modulation, buffered. FLAG set on second match.0b1100001 Reserved0b1100010 Output pulse-width modulation, buffered. FLAG set on both matches.
