
PS2
PS1
PS0
Divided By
0
0
0
1
0
0
1
2
0
1
0
4
0
1
1
8
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Table 9. Prescaler DivisionFactors
TSCR
Imer 1&2 Status ControlRegisters
DAH Timer 1, DCH Timer 2,
Read/ Write
D7 D6 D5 D4 D3 D2 D1 D0
PS0 =PrescalerMux. Select
PS1 =PrescalerMux. Select
PS2 =PrescalerMux. Select
PSI =PrescalerInitialize Bit
D4 = TimersEnable Bit
*
D5 = TimersEnable Bit
*
ETI = Enable TimerInterrupt
TMZ = TimerZero Bit
*
Only Available in TSCR1
Figure32. Timer Status Control Registers
TIMERS
(Continued)
TMZ.
Low-to-high transitionindicatesthatthetimer
count register has decrement to zero. This
must be cleared by user software before to start
with a newcount.
ETI.
This bit, when set, enablesthe timer interrupt
(vector#3forTimer1,vector#1forTimer2)request.
If ETI=0the timer interruptis disabled.IfETI=1 and
TMZ= 1an interruptrequestis generated.
D5.
This is the timers enable bit D5. It must be
cleared to0 togetherwith aset to 1 of bit D4 to en-
able both Timer 1 and Timer 2 functions. It is not
implemented on TSCR2 register.
D4.
This is the timers enable bit D4. This bit must
be setto 1 togetherwith aclear to 0 of bitD5 to en-
able both Timer 1 and Timer 2 functions. It is not
implemented on TSCR2 register.
bit
D5
D4
Timers
0
0
Disabled
0
1
Enabled
1
X
Reserved
PS1.
Used to initialize the prescaler and inhibit its
countingwhile PSI = 0 the prescaler is set to 7FH
andthe counteris inhibited.When PSI=1 the pres-
caler is enabled to count downwards. As long as
PSI=0 bothcounterand prescalerarenotrunning.
PS2-PS0.
Thesebits select thedivision ratioof the
prescaler register.(see table 9)
The TSCR1 and TSCR2 registers are cleared on
reset. The correct D4-D5 combination must be
written in TSCR1 by user’s software to enable the
operation of Timer 1 andTimer 2.
TCR
Timer Counter1&2 Register
D3H Timer 1,DBH Timer 2, Read/ Write
D7 D6 D5 D4 D3 D2 D1 D0
D7 -D0 =Counter bits
Figure 33. Timer CounterRegisters
PSC
TimerPrescaler 1&2 Register
D2H Timer 1,DAH Timer 2, Read/ Write
D7 D6 D5 D4 D3 D2 D1 D0
D6 -D0 =Prescalerbits
Always read as “0”
Figure 34. Timer CounterRegisters
ST6369
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