mc68hc708mp16 Freescale Semiconductor, Inc, mc68hc708mp16 Datasheet - Page 232

• Manufacturer Part Number: mc68hc708mp16
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Timer Interface Module B (TIMB)
12.4.4 Pulse Width Modulation (PWM)
Technical Data
232
NOTE:
Channels 2 and 3 can be linked to form a buffered output compare
channel whose output appears on the PTE6/TCH2B pin. The TIMB
channel registers of the linked pair alternately control the output.
Setting the MS2B bit in TIMB channel 2 status and control register
(TBSC2) links channel 2 and channel 3. The output compare value in the
TIMB channel 2 registers initially controls the output on the
PTE6/TCH2B pin. Writing to the TIMB channel 3 registers enables the
TIMB channel 3 registers to synchronously control the output after the
TIMB overflows. At each subsequent overflow, the TIMB channel
registers (2 or 3) that control the output are the ones written to last.
TBSC2 controls and monitors the buffered output compare function, and
TIMB channel 3 status and control register (TBSC3) is unused. While the
MS2B bit is set, the channel 3 pin, PTE7/TCH3B, is available as a
general-purpose I/O pin.
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. Writing to the active
channel registers is the same as generating unbuffered output
compares.
By using the toggle-on-overflow feature with an output compare channel,
the TIMB can generate a PWM signal. The value in the TIMB counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIMB counter
modulo registers. The time between overflows is the period of the PWM
signal.
As
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIMB to clear the channel pin on output compare if the state of the PWM
pulse is logic 1. Program the TIMB to set the pin if the state of the PWM
pulse is logic 0.
Figure 12-3
Timer Interface Module B (TIMB)
shows, the output compare value in the TIMB channel
MC68HC708MP16
Freescale Semiconductor
—
Rev. 3.1