NXP Semiconductors MPC5644A, Reference Manual, Page: 887 / 1735

Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 887
Figure 24-49. TCR1 Clock Selection
24.5.6.1.2 Internally clocked mode
TCR1 can be driven by the system clock or system clock divided by 2, before the prescaler. TCR1 can also
be clocked by a Peripheral Timebase Clock generated within the MCU, also selected by TCR1CTL. The
maximum frequency of the Peripheral Timebase Clock is system clock divided by two. TCR1 advances
only on the rising edges of the Peripheral Timebase Clock. The use of this clock is MCU-dependent.
TCR1CTL can also be used to freeze TCR1 clock independently of TCR2 (unlike GTBE).
24.5.6.1.3 TCR1 clock prescaling
Any clock source selected by TCR1CTL is prescaled by a factor of 1 to 256, selected by ETPU_TBCR
field TCR1P. For more information on prescaler configuration refer to
Section 24.4.3.1, ETPU_TBCR –
eTPU Time Base Configuration Register . The TCR1 Prescaler resets when etpu_gtbe_in is negated. After
reset, it starts counting up to TCR1P when etpu_gtbe_in is asserted. When TCR1 increments
(etpu_gtbe_in = 1), the prescaler starts a new count and the new TCR1P becomes effective. When TCR1
is written by microcode, the prescaler is reloaded with TCR1P and it becomes effective, if etpu_gtbe_in is
asserted.
24.5.6.1.4 STAC bus client mode
In this mode the TCR1 register is continuously updated from the STAC bus, and the clock selection and
prescaling logic becomes ineffective. It is not writable by the microcode, and when read, it reflects the
STAC bus imported value. The use of EAC is forbidden in client mode. This mode is configured through
the register ETPU_REDCR (see
Section 24.4.3.4, ETPU_REDCR – eTPU STAC Configuration Register ).
24.5.6.1.5 STAC bus server mode
TCR1 bus can be exported to the STAC bus as a server, providing time information to other peripherals.
This mode is configured through the register ETPU_REDCR (see
Section 24.4.3.4, ETPU_REDCR –
eTPU STAC Configuration Register ).
24.5.6.2 Timer Count Register 2 – TCR2
The TCR2 is a 24-bit counter which can be used in the following modes:
• Pin Transition Mode: Count the rise, fall or both transitions of TCRCLK signal.
TCR1CTL
TCR1
System
10
00
TCRCLK Prescaler
Input Originated
TCR1
Prescaler
In TCRCLK pin,
after the filter
1,2,3,..,256
TCR1P
8
01
Peripheral Timebase Clock
Red Line (STAC) bus
11
no clock
0
1
div 2
TCR1CS
Clock