MPC563XM Reference Manual, Rev. 1
816
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
value to occur while the new match value is being written. The set of the MRLE due to match
reprogramming prevails over the MRLE clear, thus allowing the new programmed match to occur.
23.4.5.3
Transition Detection and Time Base Capture
Time Base Capture(s) occur when the value of a specified TCR is sampled into the Capture1 and/or
Capture2 register. TBS1[1] and TBS2[1] select which TCR will be captured in Capture 1 and Capture2,
respectively.
A capture event may occur due to either of the following events:
•
the assertion condition of Match Recognition Latch (MRL), even if MRL is simultaneously
negated by microcode
•
the assertion condition of Transition Detection Latch (TDL), even if TDL is simultaneously
negated by microcode.
•
any Transition Event specified by IPAC1 if both the Transition Detection Latch TDL1 and
Transition Continuous Capture Enable TCCE1 are asserted.
A capture event occurs together with the assertion of MRL or TDL either on T2 or T4 positive edges, and
captures the time-base value that caused the match, even if TCR1/2 increments concurrently with the
assertion (see
Section 23.6.1, “Microcycle and I/O Timing
)
1
. MRL1/2 and TDL1 may, depending on the
channel mode, inhibit the capture of the second event’s TCR into Capture1/2. As a general rule, values
captured by signal transitions are not overwritten by values captured by match events.
When the enable bit TCCE1 is asserted, captures due to Transition Events also occur after TDL1 is
asserted. Those captures happen on transition events specified by IPAC1, and the TCR value is saved into
Capture1 register only.
The capturing scheme is defined by the Channel Mode programmed at register PDCM, or at register
UDCM when User Defined Channel Mode is selected. For more information on mode-dependent capture
schemes refer to
Section 23.4.5.4, “Channel Modes
23.4.5.3.1
TDL1/2 - Transition Detect Latches
TDL1/2 indicate detection of specific transition occurrences on a channel input signal. TDL1 and TDL2
assertion causes service request in single and double transition predefined modes, respectively. TDL2
assertion does not cause Service Request in single transition predefined modes, and TDL1 assertion does
not cause Service request in double transition predefined modes. In single transition channel predefined
modes TDL2 can be asserted on the second transition, but does not generate Service Request. Yet on
predefined modes, TDL2 assertion is enabled only if TDL1 is asserted to detect an ordered input signal
double transition. All the restrictions above, however, may be overridden by using the User Defined
Channel Mode. The IPAC1 and IPAC2 registers indicate the programmed edges of the first and second
detected transition, respectively.
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 IPAC1/2 programming (see
OPAC1,OPAC2 - Input and Output Pin Action Control Registers
). When using a channel mode where the
1.
In TPU3, when TCR1 was counting at maximum rate of system clock divided by 2, the next value was captured.