SN8P2740 Series
ADC, OP-amp, Comparator 8-Bit Micro-Controller
9.2 NORMAL COMPARATOR MODE
Comparator pins are shared with GPIO controlled by CM0EN bit. When CM0EN=1, CM0N pin is enabled connected to
comparator negative terminal, and CM0P pin is enabled connected to comparator positive terminal. CM0OEN controls
comparator output connected to GPIO or not. When CM0OEN=1, comparator output terminal is connected to CM0O
pin and isolate GPIO function. When CM0OEN=0, comparator output status can be read through CM0OUT flag and
CM0O pin is GPIO mode.
CM0P
CM0N
CM0O
CM0P
CM0N
+
+
Comparator
Internal Logic
Comparator
Internal Logic
Comparator
Comparator
-
-
CM0O = GPIO
CM0EN = 1, CM0OEN = 1
CM0EN = 1, CM0OEN = 0
Note: The comparator enable condition is fixed CM0EN=1, or the comparator pins are GPIO mode and
comparator is disabled.
The CM0OUT and CM0IRQ bits indicate the comparator result. The CM0OUT shows the comparator result
immediately, but the CM0IRQ only indicates the event of the comparator result. The event condition is controlled by
register and includes rising edge (CM0OUT changes from low to high) and falling edge (CM0OUT changes from high
to low) controlled by CM0G bit. When CM0G = 0, the comparator 0 interrupt trigger direction is falling edge. When
CM0G = 1, the comparator 0 interrupt trigger direction is rising edge.
Note: CM0OUT is comparator raw output without latch. It varies depend on the comparator process
result. But the CM0IRQ is latch comparator output result. It must be cleared by program.
Comparator supports interrupt function. The interrupt trigger condition can be selected through CM0G bit including
rising edge and falling edge. If CM0G = 0, comparator output trigger edge is falling edge. If CM0G = 1, comparator
output trigger edge is rising edge. The edge detection is from comparator output signal through delay processor. When
comparator output edge event occurs and equal CM0G condition, CM0IRQ flag is issued. If CM0IEN = 1, program
counter points to interrupt vector to execute interrupt service routine.
CM0OUT
CM0IRQ, CM0G=0 falling edge
CM0IRQ sets as falling edge.
CM0IRQ sets as falling edge.
CM0IRQ, CM0G=1 rising edge
CM0IRQ sets as rising edge. CM0IRQ sets as rising edge.
*. CM0IRQ is cleared by program.
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