NXP Semiconductors MPC5644A, Справочное руководство, Страница: 841 / 1735

Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 841
combined with Function microcode (and optionally Angle Mode logic) to implement Channel I/O
functionality.
eTPU’s Enhanced Channels are capable of dual action , meaning that each channel logic can handle two
events at different times and/or cause two separated actions—these actions and events can be mutually
dependent (with the first either blocking or enabling the other), or both independent, depending on the
programmed
Channel Mode .
Each Enhanced Channel contains event logic containing two Event Register sets , each set supporting one
input and/or output action, the pair implementing dual-action support. Each Event Register set contains
two 24 bit registers: Match and Capture. The
Match register holds the pending match value which is
compared against one of the two time bases by an equal-only/greater-equal comparator. The Capture
register captures one of the two time bases as a result of a Match or Transition detection. Service Requests
are issued on particular combination of match and capture events, defined by the selected Channel Mode.
In the context of the eTPU channels, a Match is a comparison between a time base value and a channel
Match register. If those two values are coincident, or the time base value is greater than the value of the
Match register, a
Match Event occurs . Depending on the channel mode of operation and current state of
the channel logic, the match event may be recognized, i.e., change the state of the channel, or be ignored.
A match event recognized by the channel logic is called a
Match Recognition . Match Recognitions can
cause, also depending on Channel Mode and current state, the channel to request service, configuring a
Match Service Request .
eTPU uses two kinds of comparator to assert a Match Event: an Equal comparator , in which both the
Match Register and the value of the selected time base must match exactly, and a Greater-Equal
comparator . The Greater-Equal comparator considers any time base value between the range [N:
N+0x800000-1] as a valid match against the value of N in the Match Register, even when the value
N+0x800000-1 wraps around the point of origin (0x0). Refer to
Figure 24-35 for an illustration of the
matching values on a Greater-Equal comparator.
The second source of events for the eTPU channel is a Transition detected at the corresponding channel’s
input signal. Two distinct Transition detections can be programmed individually for each channel,
allowing recognition of all possible combinations of edge detection. It is also possible to check the
sampled state of an input signal upon the occurrence of a Match: the sampling of the expected value is
treated as a Transition, even if the input signal did not necessarily toggled at the time of the Match, or at
any time at all.
Like Match Events, Transitions Events may or not be recognized by the channel logic. When they are, a
Transition Detection occurs. As well as Match Recognitions, Transition Detections can issue a Channel
Service Request, depending on Channel Mode and current state.
Transition Detections and Match Recognitions are sometimes simply called Transitions and Matches
throughout this document, for short.
Input and output signals can be processed separately by the channel logic and microcode, and can also be
combined such that Matches and Transitions are used to cause
output signal actions . The output signals
can also be directly controlled by microcode. Many event combinations are allowed for a channel, given
the possibility of configuring pairs of matches and transitions for the dual-action logic, where each event