Motorola MC6805R Series - Page 34

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