C8051F52X Datasheet, PDF (71/220 Pages) Silicon Laboratories – 8/4/2 kB ISP Flash MCU Family

C8051F52x-53x
programmed, 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 “11. Interrupt Handler” on page 91). The CP0FIF flag is set to
logic 1 upon a Comparator falling-edge detect, and the CPnRIF flag is set to logic 1 upon the Comparator
rising-edge detect. Once set, these bits remain set until cleared by software. The output state of the Com-
parator can be obtained at any time by reading the CPnOUT bit. The Comparator is enabled by setting the
CP0EN bit to logic 1, and is disabled by clearing this bit to logic 0.
The output state of the Comparator can be obtained at any time by reading the CP0OUT bit. The Compar-
ator is enabled by setting the CP0EN bit to logic 1, and is disabled by clearing this bit to logic 0. When the
Comparator is enabled, the internal oscillator is awakened from SUSPEND mode if the Comparator output
is logic 0.
Note that false rising edges and falling edges can be detected when the comparator is first powered-on or
if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the
rising-edge and falling-edge flags be explicitly cleared to logic 0 a short time after the comparator is
enabled or its mode bits have been changed. This Power Up Time is specified in Table 8.1 on page 74.
SFR Definition 8.1. CPT0CN: Comparator0 Control
R/W
CP0EN
Bit7
R
CP0OUT
Bit6
R/W
CP0RIF
Bit5
R/W
CP0FIF
Bit4
R/W
R/W
R/W
R/W
Reset Value
CP0HYP1 CP0HYP0 CP0HYN1 CP0HYN0 00000000
Bit3
Bit2
Bit1
Bit0 SFR Address:
0x9B
Bit7: CP0EN: Comparator0 Enable Bit.
0: Comparator0 Disabled.
1: Comparator0 Enabled.
Bit6: CP0OUT: Comparator0 Output State Flag.
0: Voltage on CP0+ < CP0–.
1: Voltage on CP0+ > CP0–.
Bit5: CP0RIF: Comparator0 Rising-Edge Flag.
0: No Comparator0 Rising Edge has occurred since this flag was last cleared.
1: Comparator0 Rising Edge has occurred.
Bit4: CP0FIF: Comparator0 Falling-Edge Flag.
0: No Comparator0 Falling-Edge has occurred since this flag was last cleared.
1: Comparator0 Falling-Edge has occurred.
Bits3–2: CP0HYP1–0: Comparator0 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
Bits1–0: CP0HYN1–0: Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
Rev. 0.3
71