mc68hc05j5ap Freescale Semiconductor, Inc, mc68hc05j5ap Datasheet - Page 60

• Manufacturer Part Number: mc68hc05j5ap
• Description: General Description The Mc68hc05j5a Is A Member Of The Low-cost High-performance M68hc05 Family Of 8-bit Microcontroller Units Mcus . The M68hc05 Family Is Based On The Customer-speci Ed Integrated Circuit Design Strategy. All Mcus In The Family
• Manufacturer: Freescale Semiconductor, Inc

GENERAL RELEASE SPECIFICATION
9.1
9-2
RESET
TCNTH
The basis of the 16-bit Timer is a 16-bit free-running counter which increases in
count with each internal bus clock cycle. The counter is the timing reference for
the input capture and output compare functions. The input capture and output
compare functions provide a means to latch the times at which external events
occur, to measure input waveforms, and to generate output waveforms and timing
delays. Software can read the value in the 16-bit free-running counter at any time
without affect the counter sequence.
Because of the 16-bit timer architecture, the I/O registers are pairs of 8-bit regis-
ters. Each register pair contains the high and low byte of that function. Generally,
accessing the low byte of a specific timer function allows full control of that func-
tion; however, an access of the high byte inhibits that specific timer function until
the low byte is also accessed.
Because the counter is 16 bits long and preceded by a fixed divide-by-four pres-
caler, the counter rolls over every 262,144 internal clock cycles. Timer resolution
with a 4MHz crystal oscillator is 2 microsecond/count.
The interrupt capability and the input capture edge are controlled by the timer con-
trol register (T1CR) located at $0012 and the status of the interrupt flags can be
read from the timer status register (T1SR) located at $0013.
TIMER1 COUNTER REGISTERS (TCNTH, TCNTL)
The functional block diagram of the 16-bit free-running timer counter and timer
registers is shown in Figure 9-2. The timer registers include a transparent buffer
latch on the LSB of the 16-bit timer counter.
READ
Figure 9-2. 16-Bit Timer Counter Block Diagram
($FFFC)
READ
$12
Freescale Semiconductor, Inc.
TIMER1 CONTROL REG.
For More Information On This Product,
TCNTH ($18)
OVERFLOW (T1OF)
Go to: www.freescale.com
LATCH
16-BIT COUNTER
16-BIT TIMER
July 16, 1999
TCNTL ($19)
TCNTL LSB
TIMER1 STATUS REG.
$13
4
INTERNAL
INTERRUPT
TCNTL
READ
(f
REQUEST
INTERNAL
CLOCK
OSC
TIMER1
MC68HC05J5A
DATA
BUS
2)
REV 2.1