MC68HC05B4 Datasheet, PDF (65/298 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

ICF2 — Input capture flag 2
This bit is set when a negative edge is detected by the input capture edge detector 2 at TCAP2;
an input capture interrupt will be generated if ICIE is set. ICF2 is cleared by reading the TSR and
then the input capture low register 2 ($1D).
1 (set) – A valid (negative) input capture has occurred.
0 (clear) – No input capture has occurred.
OCF2 — Output compare flag 2
This bit is set when the output compare 2 register contents match those of the free-running
counter; an output compare interrupt will be generated if OCIE is set. OCF2 is cleared by reading
the TSR and then reading or writing the output compare 2 low register ($1F).
5
1 (set) – A valid output compare has occurred.
0 (clear) – No output compare has occurred.
5.3
Input capture
‘Input capture’ is a technique whereby an external signal is used to trigger a read of the free
running counter. In this way it is possible to relate the timing of an external signal to the internal
counter value, and hence to elapsed time.
There are two input capture registers: input capture register 1 (ICR1) and input capture register 2 (ICR2).
The same input capture interrupt enable bit (ICIE) is used for the two input captures.
5.3.1 Input capture register 1 (ICR1)
Input capture high 1
Input capture low 1
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$0014
Undefined
$0015
Undefined
The two 8-bit registers that make up the 16-bit input capture register 1 are read-only, and are used
to latch the value of the free-running counter after the input capture edge detector circuit 1 senses
a valid transition at TCAP1. The level transition that triggers the counter transfer is defined by the
input edge bit (IEDG1). When an input capture 1 occurs, the corresponding flag ICF1 in TSR is set.
An interrupt can also accompany an input capture 1 provided the ICIE bit in TCR is set. The 8 most
significant bits are stored in the input capture high 1 register at $14, the 8 least significant bits in
the input capture low 1 register at $15.
MC68HC05B6
Rev. 4
PROGRAMMABLE TIMER
TPG
MOTOROLA
5-7