NXP Semiconductors MPC5644A, Reference Manual, Page: 859 / 1735

Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 859
The sampling of a determined value (0 or 1) on the input signal due the occurrence of a Match is also
treated as a “transition”, depending on IPACA/B programming (see
Section , IPACA,IPACB and
OPACA,OPACB – Input and Output Pin Action Control Registers ). When using a channel mode where
the transition1 is initially blocked and IPACA is programmed to detect such “transitions”, the occurrence
of a Match A only unblocks the transition after the sampling. It means that the transition on the first Match
(IPACA configurations 100 and 101) is not effective on predefined modes where Transition A is enabled
by Match A (m2_st, m2_dt, m2_o_st and m2_o_dt) or user-defined modes with UDCM bit M1ET
asserted. A Transition A can still happen after the Match A, however, if MatchA register is reprogrammed
without clearing MRLA.
TDLA/B assertion conditions initiates a capture event of one or both selected TCR buses. TDLA or TDLB
transition event generates a Service Request, depending on channel mode, previous events and the state of
SRI. For more information on the service request scheme, refer to
Section 24.5.1.1.2, Entry point address
generation , and Section 24.5.5.4, Channel Modes .
Assertion of TDLA/B occurs on either T2 or T4 positive edges. The capture event occurs on the same
clock, and captures the time base value present when TDLA/B was asserted
1
. TDLA and TDLB are
negated during reset and may also be negated independently by microcode. TDLA/B is reset by no way
other than reset and microcode.
It is the transition from 0 to 1 in TDL that causes the Transition actions: even if TDL assert conditions are
satisfied, no action due to a Transition occurs if TDL was already set to 1. However, if a Transition and a
microoperation negating TDLs occur at the same time and TDL was already negated, TDL negation by
microcode overrides its assertion, but any dependable captures and pin action occurs anyway.
24.5.5.3.2 TCCEA – Transition Continuous Capture Enable
TCCEA enables capture from transitions after the TDLA flag is set. TCCEA is negated on reset, so that a
capture occurs only when TDLA asserts. TCCEA can be set and reset by microcode only, through the
instruction field MTD (see
Section 24.5.9.3.8, Disable match and transition service requests ). It can only
be set together with inhibiting of the channel service requests (SRI = 1)
1
.
When TCCEA is asserted, the transition events specified by IPACA that occur after TDLA is set also cause
captures into the CaptureA register only. However, output actions related to transition events are still
blocked by TDLA.
24.5.5.4 Channel Modes
The Enhanced Channels support various modes of operation combining Match A/B recognition and
transition detection events which set MRLA/B and TDLA/B. The channel mode is individually set for each
channel by eTPU microcode, through the PDCM register (see
Section , PDCM – Predefined Channel
Mode ). The PDCM register selects among a set of 13 predefined channel modes, and also a user-defined
channel mode.
The order in which events occur, combined with assigned channel mode, establish which following event
detections are inhibited and/or enabled, as well as the actions taken: Time Base capture, flag setting
(MRLA/B, TDLA/B), match disabling (MRLEA/B), output signal transition, and Service Request. Those
1.TCCEA provides compatibility with TPU when service request is inhibited.