W925E240 Datasheet, PDF (47/73 Pages) Winbond – 8-BIT CID MICROCONTROLLER

W925E/C240
6.10 Comparator
A built-in comparator can compare the analog signal. There is an analog input paths from pin VNEG.
Two reference inputs; one is from pin VPOS and other is from regulator output. When the voltage of
positive input is higher than the negative input, the comparator output will be high. The
RESEC(COMPR.3) is the result of the comparison. An internal rising signal on RESC produces
interrupt flag of COMPF (EXIF.4). The flag COMPF is cleared when comparator interrupt routine is
executed or cleared by software. Set COMPEN to enable the comparator function.
VNEG(P4.2)
VPOS(P4.4)
REF1
REF
X.XV
REGULATOR
EN
C3
RESET
D
CK
Clr
D
RESC _CK
Clr
COMPF=0
COMPEN
SCON1.5(REGON)
EXIF.4
(COMPF)
Figure 6-10 The Configuration of Comparator
The output voltage of the regulator is tunable by 4 bits in regulator voltage control register (REGVC).
When REGVC is equal to 0AH, the output voltage is 1.0V. The higher value of REGVC the lower
voltage output of regulator. The adjustable voltage range is about from 0.72V to 1.48V. The variation
of the voltage depends on the V_DD. Following is the table of REGVC vs. regulator voltage.
Regvc 00 01 02 03 04 05 06 07 08 09 0ah 0bh 0ch 0dh 0eh 0fh
No
Loading(3V)
1.497
1.4464
1.3941
1.3426
1.2899
1.238
1.186
1.1352
1.081
1.029
0.976
0.924
0.869
0.815
0.762
0.7112
No
Loading(5V)
1.500
1.449
1.397
1.345
1.292
1.241 1.188 1.137
1.083 1.031 0.978 0.925 0.87
0.816 0.763 0.712
6.11 DTMF Generator
W925E/C240 provides a DTMF generator, which outputs the dual tone multi-frequency signal to the
DTMF pin. The DTMF generator can work well at the operating frequency of 3.58MHz. A DTMF
generator register DTMFG controls the DTMF output and specifies the desired low/high frequency.
The tones are divided into two groups (low group and high group). When the generator is disable, the
DTMF pin is in tri-state. The relation between the DTMF signal and the corresponding touch-tone
keypad is shown in Figure 6-11.
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Publication Release Date: July 12, 2005
Revision A10