Timer
Pin
Internal
l/J2
Clock
(fosc+
41
fplN - Prescaler Input Frequency
fCIN-Counter
Input Frequency
8
Timer Data Register (TDR)
8-Bit
Counter
7-Bit Prescaler
Select
t-
_______
-t
1
-
of
-
8
3
Timer Control Register Bits:
Set
TIR-
Timer Interrupt Request Status
TIM-
Timer Interrupt Mask
TIN-
Timer Input Select
TIE-
Timer External Input Enable
PSC-
Prescaler Clear
PS2,
PS
1,
PSO-
Prescaler Select
Timer Control Register
(TCR)
Mask Option Register Bits:
ClK-Clock
Oscillator Type
TOPT - Timer Mask/Programmable Option
CLS
- Timer Clock Source
P2,
Pl,
PO
- Prescaler Option
NOTE:
The
TOPT
bit in the mask option register selects whether the timer
~s
software programmable
via
the timer control register or
emulates the mask programmable parts
via
the
MOR
EPROM
byte.
Figure
5-3.
MC68705R3/MC68705U3
Timer
Block
Diagram