NXP Semiconductors MPC5644A, Reference Manual, Page: 845 / 1735

Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 845
• A Time Base Selection register (TBSA or TBSB)
• A Match Recognition status flag (or latch) (MRLA or MRLB)
• A Match Recognition Enable latch (MRLEA or MRLEB)
• A Transition Detection flag (or latch) (TDLA or TDLB)
• A Transition Continuous Capture enable (TCCEA only)
ERA and ERB are associated with the first and second events in double action modes, not necessarily in
that order. The order of Match events associated with ERA and ERB depends on the programmed channel
mode, the MatchA and MatchB values, and the timebases selected by TBSA and TBSB. Similarly, the
order of Transition events associated with ERA and ERB depends on the programmed channel mode, and
the transition detection selected by IPACA and IPACB.
These registers are directly or indirectly accessed by the microcode. TBSA and TBSB registers are defined
in
Section , TBSA and TBSB – Time Base Selection Registers . The other registers are explained in
Section 24.5.5.2, Match Recognition and Section 24.5.5.3, Transition Detection and Time Base Capture .
Access to the Event Registers is qualified by the channel currently selected by the microengine (i.e., the
channel value currently in the CHAN register). During the channel transition period (automatic CHAN
assignment), or whenever CHAN is written by microcode, Capture values of the new selected channel are
sampled into Microengine registers ERTA and ERTB, therefore becoming visible to the microcode. At the
same time, updated values of MRLA, MRLB, TDLA and TDLB are sampled into the branch logic, making
the register values and the flags coherent with respect to each other and with the thread selected by the
Scheduler
1
.
NOTE
The Function Mode bits are also sampled from the Host interface on Time
Slot Transition, so that they remain constant to microengine even when Host
changes them.
During service, the microcode can access updated values of the Event Registers of any channel by writing
the channel number to CHAN. Writing CHAN with the same value (CHAN := CHAN) updates ERTA and
ERTB with the new captured values, the branch logic with updated MRLA/B and TDLA/B flags. Writing
CHAN with a different value does the same with the values from the newly selected channel.
Match values are also accessed through ERTA and ERTB Microengine registers, which are copied to/from
the channel MatchA and MatchB registers by specific microinstruction operations.
Microcode writes to the flags and selections (MRLA/B, TDLA/B and TBSA/B) are immediately effective
to the channel. The MRLA/B and TDLA/B branch conditions are also immediately reset when their
correspondent flags are reset by microcode. Match registers are indirectly written by microcode through
ERTA/B. MRLEA/B is unconditionally asserted when respective Match register is updated from ERTA/B,
and its negation is immediate.
Table 24-41 summarizes Event Registers accesses.
1. The thread selected is determined by the Entry Point which, in turn, is determined partially by the channel latches. See
Section 24.5.1.1.2, Entry point address generation .