Rainbow Electronics ATAR862-3 - Manual (Page 45)

45
ATAR862-3
4556B–4BMCU–02/03
Figure 37. Timer 2
Timer 2 Modes
Mode 1: 12-bit Compare
Counter The 4-bit stage and the 8-bit stage work together as a 12-bit compare counter. A com-
pare match signal of the 4-bit and the 8-bit stage generates the signal for the counter
reset, toggle flip-flop or interrupt. The compare action is programmable via the compare
mode register (T2CM). The 4-bit counter overflow (OVF1) supplies the clock output
(POUT) with clocks. The duty cycle generator (DCG) has to be bypassed in this mode.
Figure 38. 12-bit Compare Counter
Mode 2: 8-bit Compare
Counter with 4-bit
Programmable Prescaler Figure 39. 8-bit Compare Counter
The 4-bit stage is used as programmable prescaler for the 8-bit counter stage. In this
mode, a duty cycle stage is also available. This stage can be used as an additional 2-bit
prescaler or for generating duty cycles of 25%, 33% and 50%. The 4-bit compare output
(CM1) supplies the clock output (POUT) with clocks.
4-bit Counter 2/1
RES OVF1
Compare 2/1
T2CO1
CM1
POUT
SSI POUT
CL2/2
DCG
T2M1 P4CR
8-bit Counter 2/2
RES OVF2
Compare 2/2
T2CO2 T2CM
Control
TOG2
INT4
Biphase-,
Manchester-
modulator
OUTPUT
MOUT
M2
to
Modulator 3
T2O
Timer 2
modulator
output-stage
T2M2
SO Control
SSI SSI
I/O-bus
T2C
CL2/1
T2I
SYSCL
T1OUT
TOG3
SCL
I/O-bus
DCGO
4-bit counter
4-bit compare
RES
4-bit register
CM1
POUT (CL2/1 /16)
8-bit counter
8-bit compare
8-bit register
OVF2
CM2
RES
T2RM T2OTM
Timer 2
output mode
and T2OTM-bit
T2IM T2CTM
TOG2
INT4
CL2/1
DCG
T2D1, 0
4-bit counter
4-bit compare
RES
4-bit register
CM1
POUT
8-bit counter
8-bit compare
8-bit register
OVF2
CM2
RES
T2RM T2OTM
Timer 2
output mode
and T2OTM-bit
T2IM T2CTM
TOG2
INT4
CL2/1
DCG
T2D1, 0
DCGO