PIC18F23K22-ESLASHML datasheet(198/496 Pages) MICROCHIP

198 / 496 page

PIC18(L)F2X/4XK22

DS41412C-page 198

Preliminary

 2010 Microchip Technology Inc.

14.4.6

PWM STEERING MODE

In Single Output mode, PWM steering allows any of the

PWM pins to be the modulated signal. Additionally, the

same PWM signal can be simultaneously available on

multiple pins.

Once

the

Single

Output

mode

selected

(CCPxM<3:2> = 11 and PxM<1:0> = 00 of the

CCPxCON register), the user firmware can bring out

the same PWM signal to one, two, three or four output

pins by setting the appropriate Steering Enable bits

(STRxA, STRxB, STRxC and/or STRxD) of the

PSTRxCON register, as shown in Table 14-13.

While the PWM Steering mode is active, CCPxM<1:0>

bits of the CCPxCON register select the PWM output

polarity for the PxD, PxC, PxB and PxA pins.

The PWM auto-shutdown operation also applies to

PWM Steering mode as described in Section 14.4.3

“Enhanced PWM Auto-shutdown Mode”. An auto-

shutdown event will only affect pins that have PWM

outputs enabled.

FIGURE 14-18:

SIMPLIFIED STEERING

BLOCK DIAGRAM

14.4.6.1

Steering Synchronization

The STRxSYNC bit of the PSTRxCON register gives

the user two selections of when the steering event will

happen. When the STRxSYNC bit is ‘0’, the steering

event will happen at the end of the instruction that

writes to the PSTRxCON register. In this case, the

output signal at the PxA, PxB, PxC and PxD pins may

be an incomplete PWM waveform. This operation is

useful when the user firmware needs to immediately

remove a PWM signal from the pin.

When the STRxSYNC bit is ‘1’, the effective steering

update will happen at the beginning of the next PWM

period. In this case, steering on/off the PWM output will

always produce a complete PWM waveform.

Figures 14-19 and 14-20 illustrate the timing diagrams

of the PWM steering depending on the STRxSYNC

setting.

Note:

The associated TRIS bits must be set to

output (‘0’) to enable the pin output driver

in order to see the PWM signal on the pin.

TRIS

PxA pin

PORT Data

PxA Signal

STRxA

TRIS

PxB pin

PORT Data

STRxB

TRIS

PxC pin

PORT Data

STRxC

TRIS

PxD pin

PORT Data

STRxD

Note 1: Port outputs are configured as shown when

the CCPxCON register bits PxM<1:0> = 00

and CCPxM<3:2> = 11.

2: Single PWM output requires setting at least

one of the STRx bits.

CCPxM1

CCPxM0

CCPxM1

CCPxM0

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