mc68hc05jb4p Freescale Semiconductor, Inc, mc68hc05jb4p Datasheet - Page 55

• Manufacturer Part Number: mc68hc05jb4p
• Description: Mc68hc705jb4 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

8.3
8.3.1 Timer Counter Register (TCNT) $09
8.3.2 Timer Control/Status Register (TCSR) $08
MC68HC05JB4
REV 2
MFT REGISTERS
The Timer Counter Register is a read-only register which contains the current
value of the 8-bit ripple counter at the beginning of the timer chain. This counter is
clocked at f
capture. Extended time periods can be attained using the TOF function to incre-
ment a temporary RAM storage location thereby simulating a 16-bit (or more)
counter. The value of each bit of the TCNT is shown in Figure 8-2. This register is
cleared by reset.
The TCSR contains the timer interrupt flag bits, the timer interrupt enable bits, and
the real time interrupt rate select bits. Bit 2 and bit 3 are write-only bits which will
read as logical zeros. Figure 8-3 shows the value of each bit in the TCSR follow-
ing reset.
TOF - Timer Overflow Flag
TCNT
$0009
TCSR
$0008
The TOF is a read-only flag bit.
reset:
reset:
1 = Set when the 8-bit ripple counter rolls over from $FF to $00. A
0 = Reset by writing a logical one to the TOF acknowledge bit, TOFR.
W
W
R
R
TIMER Interrupt request will be generated if TOFE is also set.
Writing to the TOF flag bit has no effect on its value. This bit is
cleared by reset.
Figure 8-3. Timer Control/Status Register (TCSR)
OP
TMR7
BIT 7
BIT 7
TOF
÷4 and can be used for various functions including a software input
0
0
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 8-2. Timer Counter Register
TMR6
BIT 6
BIT 6
RTIF
0
0
Go to: www.freescale.com
MULTI-FUNCTION TIMER
February 24, 1999
TMR5
TOFE
BIT 5
BIT 5
0
0
TMR4
BIT 4
BIT 4
RTIE
0
0
GENERAL RELEASE SPECIFICATION
TMR3
TOFR
BIT 3
BIT 3
0
0
0
RTIFR
TMR2
BIT 2
BIT 2
0
0
0
TMR1
BIT 1
BIT 1
RT1
0
1
TMR0
BIT 0
BIT 0
RT0
0
1