Enhanced Time Processing Unit (eTPU2)
Freescale Semiconductor
29-73
PXR40 Microcontroller Reference Manual, Rev. 1
29.3.5.4
GTBE - Global Time Base Enable
GTBE bit in ETPUMCR register enables time bases in both engines, allowing them to be started
synchronously. GTBE is divided in two block interface signals: etpu_gtbe_out and etpu_gtbe_in. GTBE
bit sets etpu_gtbe_out, and etpu_gtbe_in enables time bases to start. The etpu_gtbe_out signal can be used
for synchronization between eTPU time bases and time bases from other modules. If the GTBE bit in
ETPUMCR must enable only the eTPU time bases, etpu_gtbe_out is simply connected to etpu_gtbe_in.
These two cases are shown in
. Synchronization logic can be as simple as an OR or an AND
logic gate.
Once etpu_gtbe_in transitions to 1, the Engine 1 Time Bases start 1 eTPU clock earlier than Time Bases
in Engine 2, except when TCRCLK is selected as clock source or TCR1 when ETPUTBCR[TCR1CS]=1.
This happens independently of prescaler values as long as they are the same for both engines, because the
prescalers also freeze when etpu_gtbe_in = 0. Microcode can always write to TCR1/2 registers, with either
value of etpu_gtbe_in.
NOTE
The timebase prescalers are reset when the GTBE input is negated.
Figure 29-33. Time Base Synchronization
29.3.5.5
TCRCLK Digital Filter
The TCRCLK signal has an improved integrating digital filter with a 2-bit up-down counter. The counter
counts up to 3 when a high signal level is detected, or down to 0 when a low level is detected. The signal
state is updated to one when the counter stops at 3, or zero when the counter stops at 0. The field TCRCF
in register ETPUTBCR (see
Section 29.2.6.1, ETPUTBCR - eTPU Time Base Configuration Register
determines whether the TCRCLK signal input (after a synchronizer) is filtered with the same filter clock
as the channel input signals (see
Section 29.3.4.4, Enhanced Digital Filter - EDF
) or uses the eTPU clock
divided by 2, and also whether the TCRCLK digital filter works in integrator mode or the same two sample
mode as the channel filters (see
eTPU A and B
etpu_gtbe_out
tpu_gtbe_in
ETPUMCR[GTBE]
eMIOS
gtbe_out
gtbe_in
SYNCHRONIZATION BETWEEN eTPU TIME
BASES AND eMIOS TIME BASES
Summary of Contents for PXR4030
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