68HC05CT4 datasheet(96/142 Pages) FREESCALE

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Pulse Width Modulator (PWM)

General Release Specification

MC68HC05CT4 — Rev. 2.0

Pulse Width Modulator (PWM)

12.4 PWM Data Register

One PWM data register (PWMDR), located at $0020, is associated with

the PWM system. This 8-bit data register holds the duty cycle for the

PWM output; however, only six of these bits are used. PWMDR can be

written to and read at any time. Writes to the PWMDR are buffered and

are not transferred to the active register until the end of the PWM cycle

during which the write was executed.

Upon RESET the user should write to the data register prior to enabling

the PWM system (for example, prior to setting the PWME bit in the

miscellaneous control register). This avoids an erroneous duty cycle

from being driven.

PWME — Miscellaneous Control Register PWM Enable Bit

When set, this bit enables the PWM subsystem. Its main function is to

allow the user to save power when not using the PWM. When

enabled, the clocks are active to the module. When clear, this bit

shuts off the clocks to the module and relinquishes control of PC7 to

the port C logic (the PC7 pullup option should not be selected if the

PWM is used). Reset clears this bit. This bit is located in the

miscellaneous control register found in Section 13. Comparators.

Address:

$0020

Bit 7

654321

Bit 0

Read:

Write:

Reset:

Unaffected by Reset

Figure 12-3. PWM Data Register (PWMDR)

Freescale Semiconductor, Inc.

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68HC05CT4 Datasheet(PDF) 96 Page - Freescale Semiconductor, Inc