Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
144 Pulse-Width Modulator for Motor Control (PWM MC) MOTOROLA
Pulse-Width Modulator for Motor Control
For ease of software, the LDFQx bits are buffered. When the LDFQx bi ts
are changed, the reload frequency will not change until the previous
reload cycle is completed. See Figure 9-5.
NOTE: When reading the LDFQx bits, the value is the buffered value (for
example, not necessarily the value being acted upon).
Figure 9-5. Reload Frequency Change
PWMINT enables CPU interrupt requests as shown in Figure 9-6. When
this bit is set, CPU interrupt requests are generated when the PW MF bit
is set. When the PWMINT bit is clear, PWM interrupt requests are
inhibited. PWM reloads will still occur at the reload rate, but no interrupt
requests will be generated.
Figure 9-6. PWM Interrupt Requests
Table 9-2. PWM Reload Frequency
Reload Frequency Bits
LDFQ1 and LDFQ0 PWM Reload Frequency
00 Every PWM cycle
01 Every 2 PWM cycles
10 Every 4 PWM cycles
11 Every 8 PWM cycles
RELOAD RELOAD RELOAD RELOAD RELOADRELOADRELOAD
CHANGE RELOAD
FREQUENCY TO
EVERY 4 CYCLES
CHANGE RELOAD
FREQUENCY TO
EVERY CYCLE
LATCH
VDD
CPU INTERRUPT
RESET
D
CK PWMINT
PWMF
PWM RELOAD
READ PWMF AS 1,
WRITE PWMF AS 0
OR
RESET
REQUEST