MC68HC908QY1VDTE Freescale Semiconductor, MC68HC908QY1VDTE Datasheet - Page 124
Manufacturer Part Number
IC MCU 1.5K FLASH 16-TSSOP
Specifications of MC68HC908QY1VDTE
LVD, POR, PWM
Number Of I /o
Program Memory Size
1.5KB (1.5K x 8)
Program Memory Type
128 x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
-40°C ~ 105°C
Package / Case
Data Bus Width
Data Ram Size
Maximum Clock Frequency
Number Of Programmable I/os
Number Of Timers
Maximum Operating Temperature
+ 105 C
Development Tools By Supplier
FSICEBASE, M68CBL05AE, DEMO908QB8, DEMO908QC16
Minimum Operating Temperature
- 40 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Lead Free Status / Rohs Status
Timer Interface Module (TIM)
188.8.131.52 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in
pulse width value over the old value currently in the TIM channel registers.
An unsynchronized write to the TIM channel registers to change a pulse width value could cause incorrect
operation for up to two PWM periods. For example, writing a new value before the counter reaches the
old value but after the counter reaches the new value prevents any compare during that PWM period.
Also, using a TIM overflow interrupt routine to write a new, smaller pulse width value may cause the
compare to be missed. The TIM may pass the new value before it is written.
Use the following methods to synchronize unbuffered changes in the PWM pulse width on channel x:
184.108.40.206 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the TCH0 pin.
The TIM channel registers of the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1.
The TIM channel 0 registers initially control the pulse width on the TCH0 pin. Writing to the TIM channel
1 registers enables the TIM channel 1 registers to synchronously control the pulse width at the beginning
of the next PWM period. At each subsequent overflow, the TIM channel registers (0 or 1) that control the
pulse width are the ones written to last. TSC0 controls and monitors the buffered PWM function, and TIM
channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin,
TCH1, is available as a general-purpose I/O pin.
When changing to a shorter pulse width, enable channel x output compare interrupts and write the
new value in the output compare interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the PWM period to write the new
When changing to a longer pulse width, enable TIM overflow interrupts and write the new value in
the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current PWM
period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse)
could cause two output compares to occur in the same PWM period.
(PWM). The pulses are unbuffered because changing the pulse width requires writing the new
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0% duty
cycle generation and removes the ability of the channel to self-correct in the
event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
In buffered PWM signal generation, do not write new pulse width values to
the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered PWM signals.
MC68HC908QY/QT Family Data Sheet, Rev. 6
14.4.4 Pulse Width