MC908MR16CFUE Datasheet, PDF (225/282 Pages) Freescale Semiconductor, Inc – On-chip programming firmware for use with host personal computer, Clock generator module (CGM)

I/O Signals
The TIMA remains active after the execution of a WAIT instruction. In wait mode, the TIMA registers are
not accessible by the CPU. Any enabled CPU interrupt request from the TIMA can bring the MCU out of
wait mode.
If TIMA functions are not required during wait mode, reduce power consumption by stopping the TIMA
before executing the WAIT instruction.
16.6 I/O Signals
Port E shares five of its pins with the TIMA:
• PTE3/TCLKA is an external clock input to the TIMA prescaler.
• The four TIMA channel I/O pins are PTE4/TCH0A, PTE5/TCH1A, PTE6/TCH2A, and
PTE7/TCH3A.
16.6.1 TIMA Clock Pin (PTE3/TCLKA)
PTE3/TCLKA is an external clock input that can be the clock source for the TIMA counter instead of the
prescaled internal bus clock. Select the PTE3/TCLKA input by writing logic 1s to the three prescaler select
bits, PS[2:0]. See 16.7.1 TIMA Status and Control Register.
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTE3/TCLKA is available as a general-purpose I/O pin when not used as the TIMA clock input. When the
PTE3/TCLKA pin is the TIMA clock input, it is an input regardless of the state of the DDRE3 bit in data
direction register E.
16.6.2 TIMA Channel I/O Pins (PTE4/TCH0A–PTE7/TCH3A)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTE2/TCH0 and PTE4/TCH2 can be configured as buffered output compare or buffered PWM pins.
16.7 I/O Registers
These input/output (I/O) registers control and monitor TIMA operation:
• TIMA status and control register (TASC)
• TIMA control registers (TACNTH–TACNTL)
• TIMA counter modulo registers (TAMODH–TAMODL)
• TIMA channel status and control registers (TASC0, TASC1, TASC2, and TASC3)
• TIMA channel registers (TACH0H–TACH0L, TACH1H–TACH1L, TACH2H–TACH2L, and
TACH3H–TACH3L)
16.7.1 TIMA Status and Control Register
The TIMA status and control register:
• Enables TIMA overflow interrupts
• Flags TIMA overflows
• Stops the TIMA counter
• Resets the TIMA counter
• Prescales the TIMA counter clock
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
225