SN8P2740 Series
ADC, OP-amp, Comparator 8-Bit Micro-Controller
11.2 NORMAL COMPARATOR MODE
Comparator pins are shared with GPIO controlled by CM2EN bit. When CM2EN=1, CM2N pin is enabled connected to
comparator negative terminal. Comparator positive terminal is controlled by CM2RS[2:0] bits. When CM2RS[2:0]=000b,
comparator positive terminal is from CM2P pin, and GPIO function is isolated. When CM2RS[2:0]=001b~111b,
comparator positive terminal is connected to internal reference voltage source including 7-level which are 0.2*Vdd,
0.3*Vdd, 0.4*Vdd, 0.5*Vdd, 0.6*Vdd, 0.7*Vdd, 0.8*Vdd, and CM2P pin is GPIO mode. CM2OEN controls comparator
output connected to GPIO or not. When CM2OEN=1, comparator output terminal is connected to CM2O pin and isolate
GPIO function. When CM2OEN=0, comparator output status can be read through CM2OUT flag and CM2O pin is
GPIO mode.
Internal Reference
Voltage
CM2P
CM2N
CM2O
CM2P = GPIO
CM2N
+
+
Comparator
Internal Logic
Comparator
Internal Logic
Comparator
Comparator
-
-
CM2O
CM2EN = 1, CM2OEN = 1, CM2RS[2:0] = 000b
CM2EN = 1, CM2OEN = 1, CM2RS[2:0] = 001b~111b
Internal Reference
Voltage
CM2P
CM2N
CM2P = GPIO
CM2N
+
+
Comparator
Comparator
Comparator
Comparator
Internal Logic
Internal Logic
-
-
CM2O = GPIO
CM2O = GPIO
CM2EN = 1, CM2OEN = 0, CM2RS[2:0] = 000b
CM2EN = 1, CM2OEN = 0, CM2RS[2:0] = 001b~111b
Note: The comparator enable condition is fixed CM2EN=1, or the comparator pins are GPIO mode and
comparator is disabled.
The CM2OUT and CM2IRQ bits indicate the comparator result. The CM2OUT shows the comparator result
immediately, but the CM2IRQ only indicates the event of the comparator result. The event condition is controlled by
register and includes rising edge (CM2OUT changes from low to high) and falling edge (CM2OUT changes from high
to low) controlled by CM2G bit. When CM2G = 0, the comparator 2 interrupt trigger direction is falling edge. When
CM2G = 1, the comparator 2 interrupt trigger direction is rising edge.
Note: CM2OUT is comparator raw output without latch. It varies depend on the comparator process
result. But the CM2IRQ is latch comparator output result. It must be cleared by program.
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