Timer Interface B (TIMB)
I/O Registers
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information
MOTOROLA Timer Interface B (TIMB) 237
12.7.1 TIMB Clock Pin (PTE4/ATD12)
PTE4/ATD12 is an external clock input that can be the clock source for
the TIMB counter instead of the prescaled internal bus clock. Select the
PTE4/ATD12 input by writing logic 1s to the three prescaler select bits,
PS[2:0]. See 12.8.1 TIMB Status and Control Register. The minimum
TCLK pulse width, TCLKLMIN or TCLKHMIN, is:
The maximum TCLK frequency is the least: 4 MHz or bu s frequency ÷ 2.
PTE4/ATD12 is available as a general-purpose I/O pin or ADC chan nel
when not used as the TIMB clock input. When the PTE4/ATD12 pin is
the TIMB clock input, it is an input regardless of the state of the DDRE0
bit in data direction register E.
12.7.2 TIMB Channel I/O Pins (PTE1/TCH0B–PTE2/TCH1B)
Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. P TE1/TCH0B and PTE2/TCH1B
can be configured as buffered output compare or buffered PWM pins.
12.8 I/O RegistersThese input/output (I/O) registers control and monitor TIMB operat io n:
• TIMB status and control register (TBSC)
• TIMB control registers (TBCNTH–TBCNTL)
• TIMB counter modulo registers (TBMODH–TBMODL)
• TIMB channel status and control registers (TBSC0 and TBSC1)
• TIMB channel registers (TBCH0H–TBCH0L and
TBCH1H–TBCH1L)
1
bus frequency
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