Enhanced Capture Timer (ECT) Module
Timer Registers
M68HC12B Family — Rev. 9.0
Data Sheet
MOTOROLA
Enhanced Capture Timer (ECT) Module
195
By setting TFMOD in queue mode, when NOVW bit is set and the corresponding
capture and holding registers are emptied, an input capture event will first
update the related input capture register with the main timer contents. At the
next event, the TCn data is transferred to the TCnH register, the TCn is updated,
and the CnF interrupt flag is set. See Figure 13-19. In all other input capture
cases, the interrupt flag is set by a valid external event on PTn.
0 = The timer flags C3F–C0F in TFLG1 ($8E) are set when a valid input
capture transition on the corresponding port pin occurs.
1 = If in queue mode (BUFEN = 1 and LATQ = 0), the timer flags C3F–C0F
in TFLG1 ($8E) are set only when a latch on the corresponding holding
register occurs. If the queue mode is not engaged, the timer flags
C3F–C0F are set the same way as for TFMOD = 0.
PACMX — 8-Bit Pulse Accumulators Maximum Count Bit
0 = Normal operation. When the 8-bit pulse accumulator has reached the
value $FF, with the next active edge, it will be incremented to $00.
1 = When the 8-bit pulse accumulator has reached the value $FF, it will not
be incremented further. The value $FF indicates a count of 255 or more.
BUFEN — IC Buffer Enable Bit
0 = Input capture and pulse accumulator holding registers are disabled.
1 = Input capture and pulse accumulator holding registers are enabled. The
latching mode is defined by LATQ control bit. Writing a 1 into ICLAT bit
in MCCTL ($A6) when LATQ is set, will produce latching of input capture
and pulse accumulator registers into their holding registers.
LATQ — Input Control Latch or Queue Mode Enable Bit
The BUFEN control bit should be set to enable the IC and pulse accumulators’
holding registers. Otherwise, LATQ latching modes are disabled.
Writing one into ICLAT bit in MCCTL ($A6), when LATQ and BUFEN are set will
produce latching of input capture and pulse accumulators registers into their
holding registers.
0 = Queue mode of input capture is enabled. The main timer value is
memorized in the IC register by a valid input pin transition. With a new
occurrence of a capture, the value of the IC register will be transferred
to its holding register and the IC register memorizes the new timer value.
1 = Latch mode is enabled. Latching function occurs when modulus
down-counter reaches 0 or a 0 is written into the count register MCCNT
contents of IC registers and 8-bit pulse accumulators are transferred to
their holding registers. The 8-bit pulse accumulators are cleared.