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Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
890
Freescale Semiconductor
control refer to
Section 24.4.3.1, ETPU_TBCR – eTPU Time Base Configuration Register
Section 24.5.5.6, Enhanced Digital Filter – EDF
24.5.6.2.4
STAC bus client mode
In this mode the TCR2 register is continuously updated from the STAC bus, and the clock selection and
prescaling logic becomes ineffective. It is not write accessible for 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
24.5.6.2.5
STAC bus server mode
When TCR2 bus is exported to the STAC bus as a server, it can provide either time or angle bus to other
peripherals, according to its operation mode. This mode is configured through the register ETPU_REDCR
(see
Section 24.4.3.4, ETPU_REDCR – eTPU STAC Configuration Register
). To provide sequential
update of the STAC clients, the Angle tick rate must not be faster than the STAC programmed update rate.
This requirement puts a limitation on the angle clock count rate on high rate mode. In this case the Angle
and Angle Fraction accumulator (see
Section 24.5.7.4, Angle tick generator
, and
advanced at rate of system clock divided by eight. Therefore, the STAC update rate for the Angle Bus must
not be slower than eight system clocks.
24.5.6.2.6
TCR2 bus in angle clock mode
In this mode the TCR2 counter operates as part of the eTPU Angle Counter (EAC). The TCR2 bus value
reflects this angle representation in which it counts Angle Ticks. Angle Mode is selected when the AM bit
is set in ETPU_TBCR.
Note that when TCR2 works in Angle Mode, it does not count directly from the TCR2 clock input which
indicates tooth signal transition. Its Angle counter is controlled by the Count Control and High Rate logic
(see
Section 24.5.7.5, Count control and high rate logic
), which provides the interpolated pin position, and
handle cases of missing tooth, acceleration, de-acceleration and mechanical corrections.
The EAC uses the TCRCLK signal to get the tooth transition indications. The TCR2CTL field in
ETPU_TBCR has to be set for the appropriate tooth edge detection rise, fall, “rise-and-fall” or none. TCR2
count clock comes from the EAC control and not directly from the physical tooth. This way the EAC
control processes the signal transitions and handles missing teeth and flywheel mechanical corrections.
Note that when TCR2CTL selects “none” for tooth edge selection, the TCR2 is not necessarily frozen, but
can still be incremented by the EAC logic.
In Angle Mode, eTPU channel 0, 1 or 2 operation is combined with the EAC operation. When channel 0
is selected for EAC operation, the TCRCLK digital filter is used both by the EAC and by channel 0 to get
full synchronization between the two logics.
The eTPU Angle Counter (EAC) logic runs continuously and updates the TCR2 Angle counter,
eliminating the microcode latency in updating the TCR2 value.
Содержание MPC5644A
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