mc68hc705v12 Freescale Semiconductor, Inc, mc68hc705v12 Datasheet - Page 94

• Manufacturer Part Number: mc68hc705v12
• Description: M68hc05-based Mcu Hc05 Freescale Semiconductor
• Manufacturer: Freescale Semiconductor, Inc

16-Bit Timer
9.3 Timer Counter Registers $18 $19 and $1A $1B
Advance Information
The key element in the programmable timer is a 16-bit, free-running
counter or counter register preceded by a prescaler that divides the
internal processor clock by four. The prescaler gives the timer a
resolution of 2.0 microseconds if the internal bus clock is 2.0 MHz. The
counter is incremented during the low portion of the internal bus clock.
Software can read the counter at any time without affecting its value.
The double-byte, free-running counter can be read from either of two
locations, $18–$19 (counter register) or $1A–$1B (counter alternate
register). A read from only the least significant byte (LSB) of the
free-running counter ($19, $1B) receives the count value at the time of
the read. If a read of the free-running counter or counter alternate
Freescale Semiconductor, Inc.
REGISTER
TIMER
STATUS
For More Information On This Product,
$16
$17
BYTE
HIGH
ICF OCF TOF $13
OUTPUT
REGISTER
COMPARE
INTERRUPT
OUTPUT
COMPARE
CIRCUIT
CIRCUIT
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BYTE
LOW
Figure 9-1. 16-Bit Timer Block Diagram
16-Bit Timer
INTERNAL
PROCESSOR
CLOCK
INTERNAL BUS
4
ICIE
HIGH
BYTE
16-BIT FREE-
RUNNING
COUNTER
COUNTER
ALTERNATE
REGISTER
OVERFLOW
DETECT
CIRCUIT
OCIE
8-BIT
BUFFER
TOIE
LOW
BYTE
$18
$19
$1A
$1B
IEDG OLVL
BYTE
HIGH
INPUT
CAPTURE
REGISTER
EDGE
DETECT
CIRCUIT
OUTPUT
LEVEL
REGISTER
TIMER
REGISTER
BYTE
CONTROL
$12
LOW
MC68HC705V12
RESET
$14
$15
D
CLK
C
Q
LEVEL
OUTPUT
(TCMP)
PB6
—
Rev. 3.0
EDGE
INPUT
(TCAP)
PB7