mc9s08gt16a Freescale Semiconductor, Inc, mc9s08gt16a Datasheet - Page 157

• Manufacturer Part Number: mc9s08gt16a
• Description: Hcs08 Microcontrollers 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

All TPM channels are programmable independently as input capture, output compare, or buffered
edge-aligned PWM channels.
10.2
When any pin associated with the timer is configured as a timer input, a passive pullup can be enabled.
After reset, the TPM modules are disabled and all pins default to general-purpose inputs with the passive
pullups disabled.
10.2.1
When control bits CLKSB:CLKSA in the timer status and control register are set to 1:1, the prescaler and
consequently the 16-bit counter for TPMx are driven by an external clock source, TPMxCLK, connected
to an I/O pin. A synchronizer is needed between the external clock and the rest of the TPM. This
synchronizer is clocked by the bus clock so the frequency of the external source must be less than one-half
the frequency of the bus rate clock. The upper frequency limit for this external clock source is specified to
be one-fourth the bus frequency to conservatively accommodate duty cycle and phase-locked loop (PLL)
or frequency-locked loop (FLL) frequency jitter effects.
On some devices the external clock input is shared with one of the TPM channels. When a TPM channel
is shared as the external clock input, the associated TPM channel cannot use the pin. (The channel can still
be used in output compare mode as a software timer.) Also, if one of the TPM channels is used as the
external clock input, the corresponding ELSnB:ELSnA control bits must be set to 0:0 so the channel is not
trying to use the same pin.
10.2.2
Each TPM channel is associated with an I/O pin on the MCU. The function of this pin depends on the
configuration of the channel. In some cases, no pin function is needed so the pin reverts to being controlled
by general-purpose I/O controls. When a timer has control of a port pin, the port data and data direction
registers do not affect the related pin(s). See the
about shared pin functions.
10.3
The TPM includes:
Each timer channel has:
Refer to the direct-page register summary in the
assignments for all TPM registers. This section refers to registers and control bits only by their names. A
Freescale Semiconductor
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An 8-bit status and control register (TPMxSC)
A 16-bit counter (TPMxCNTH:TPMxCNTL)
A 16-bit modulo register (TPMxMODH:TPMxMODL)
An 8-bit status and control register (TPMxCnSC)
A 16-bit channel value register (TPMxCnVH:TPMxCnVL)
External Signal Description
Register Definition
External TPM Clock Sources
TPMxCHn — TPMx Channel n I/O Pins
MC9S08GT16A/GT8A Data Sheet, Rev. 1
Memory
Pins and Connections
chapter of this data sheet for the absolute address
chapter for additional information
Timer/Pulse-Width Modulator (S08TPMV2)
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