Information

gtb_out signals, represented by the example glue logic shown in the figure. Note that
these configurations are chip-dependent and implemented outside of the FTM modules.
See the chip configuration details for the chip's specific implementation.
NOTE
• In order to use the internal GTB signals to synchronize the
FTM counter of different FTM modules, the configuration
of each FTM module should guarantee that its FTM
counter starts counting as soon as the gtb_in signal is 1.
• The GTB feature does not provide continuous
synchronization of FTM counters, meaning that the FTM
counters may lose synchronization during FTM operation.
The GTB feature only allows the FTM counters to start
their operation synchronously.
35.4.28.1 Enabling the global time base (GTB)
To enable the GTB feature, follow these steps for each participating FTM module:
1. Stop the FTM counter: Write 00b to SC[CLKS].
2. Program the FTM module to the intended configuration. The operation mode needs
to be consistent across all participating modules.
3. Write 1 to CONF[GTBEEN] and write 0 to CONF[GTBEOUT] at the same time.
4. Select the intended FTM counter clock source in SC[CLKS]. The clock source needs
to be consistent across all participating modules.
5. Reset the FTM counter: Write any value to the CNT register.
To initiate the GTB feature, follow these steps for the FTM module used as the time base:
1. Write 1 to CONF[GTBEOUT].
2. If needed, configure the GTB glue logic connecting the FTM modules within the
chip. Some chips do not require configuration of glue logic. See the chip
configuration details for the chip's specific implementation.
35.5 Reset overview
The FTM is reset whenever any chip reset occurs.
When the FTM exits from reset:
• the FTM counter and the prescaler counter are zero and are stopped (CLKS[1:0] =
00b);
Reset overview
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
816 Freescale Semiconductor, Inc.