MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 216

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Timer Interface (TIM)
16.4 Functional Description
16.4.1 TIM Counter Prescaler
16.4.2 Input Capture
Advance Information
216
Figure 16-1
is the 16-bit TIM counter that can operate as a free-running counter or a
modulo up-counter. The TIM counter provides the timing reference for
the input capture and output compare functions. The TIM counter
modulo registers, TMODH–TMODL, control the modulo value of the TIM
counter. Software can read the TIM counter value at any time without
affecting the counting sequence.
The six TIM channels are programmable independently as input capture
or output compare channels.
The TIM clock source can be one of the seven prescaler outputs or the
TIM clock pin, PTD6/ATD14/TCLK. The prescaler generates seven
clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIM status and control register select the TIM clock source.
An input capture function has three basic parts: edge select logic, an
input capture latch, and a 16-bit counter. Two 8-bit registers, which make
up the 16-bit input capture register, are used to latch the value of the
free-running counter after the corresponding input capture edge detector
senses a defined transition. The polarity of the active edge is
programmable. The level transition which triggers the counter transfer is
defined by the corresponding input edge bits (ELSxB and ELSxA in
TSC0 through TSC5 control registers with x referring to the active
channel number). When an active edge occurs on the pin of an input
capture channel, the TIM latches the contents of the TIM counter into the
TIM channel registers, TCHxH:TCHxL. Input captures can generate
TIM CPU interrupt requests. Software can determine that an input
capture event has occurred by enabling input capture interrupts or by
polling the status flag bit.
shows the TIM structure. The central component of the TIM
Timer Interface (TIM)
MC68HC708AS48
MOTOROLA
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Rev. 4.0