C8051F336 Datasheet, PDF (66/234 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F336/7/8/9
The Comparator output can be polled in software, used as an interrupt source, and/or routed to a Port pin.
When routed to a Port pin, the Comparator output is available asynchronous or synchronous to the system
clock; the asynchronous output is available even in STOP mode (with no system clock active). When dis-
abled, the Comparator output (if assigned to a Port I/O pin via the Crossbar) defaults to the logic low state,
and the power supply to the comparator is turned off. See Section “20.3. Priority Crossbar Decoder” on
page 131 for details on configuring Comparator outputs via the digital Crossbar. Comparator inputs can be
externally driven from –0.25 V to (V_DD) + 0.25 V without damage or upset. The complete Comparator elec-
trical specifications are given in Table 6.12.
The Comparator response time may be configured in software via the CPT0MD register (see SFR Defini-
tion 11.2). Selecting a longer response time reduces the Comparator supply current.
CP0+
VIN+
VIN- ^CP0-
+
CP0
_
OUT
CIRCUIT CONFIGURATION
Positive Hysteresis Voltage
(Programmed with CP0HYP Bits)
VIN-
INPUTS
VIN+
Negative Hysteresis Voltage
(Programmed by CP0HYN Bits)
VOH
OUTPUT
VOL
Positive Hysteresis
Disabled
Negative Hysteresis
Disabled
Maximum
Positive Hysteresis
Maximum
Negative Hysteresis
Figure 11.2. Comparator Hysteresis Plot
The Comparator hysteresis is software-programmable via its Comparator Control register CPT0CN. The
user can program both the amount of hysteresis voltage (referred to the input voltage) and the positive and
negative-going symmetry of this hysteresis around the threshold voltage.
The Comparator hysteresis is programmed using Bits3–0 in the Comparator Control Register CPT0CN
(shown in SFR Definition 11.1). The amount of negative hysteresis voltage is determined by the settings of
the CP0HYN bits. As shown in Figure 11.2, settings of 20, 10 or 5 mV of negative hysteresis can be pro-
grammed, or negative hysteresis can be disabled. In a similar way, the amount of positive hysteresis is
determined by the setting the CP0HYP bits.
Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. (For Inter-
rupt enable and priority control, see Section “15.1. MCU Interrupt Sources and Vectors” on page 90). The
CP0FIF flag is set to logic 1 upon a Comparator falling-edge occurrence, and the CP0RIF flag is set to
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