Rainbow Electronics AT89C5132 - Manual (Page 129)

129
AT8xC5132
4173A–8051–08/02
Analog-to-Digital
Converter
The AT8xC5132 implement a 2-channel 10-bit (8 true Bits) analog-to-digital converter
(ADC). The first channel of this ADC can be used for battery monitoring while the sec-
ond channel can be used for voice sampling at 8 kHz.
Description The A/D converter interfaces with the C51 core through four special function registers:
ADCON, the ADC control register (see Table 118); ADDH and ADDL, the ADC data reg-
isters (see Table 120 and Table 121); and ADCLK, the ADC clock register (see
Table 119).
As shown in Figure 105, the ADC is composed of a 10-bit cascaded potentiometric digi-
tal to analog converter, connected to the negative input of a comparator. The output
voltage of this DAC is compared to the analog voltage stored in the Sample and Hold
and coming from AIN0 or AIN1 input depending on the channel selected (see
Table 117).
Figure 105. ADC Structure
Figure 106 shows the timing diagram of a complete conversion. For simplicity, the figure
depicts the waveforms in idealized form and does not provide precise timing informa-
tion. For ADC characteristics and timing parameters refer to the Section “AC
Characteristics”.
Figure 106. Timing Diagram
0
1
AIN1
AIN0
ADCS
ADCON.0
AVSS
Sample and Hold
ADDH
AREFP
R/2R DAC
ADC
CLOCK
AREFN
8
10
ADEN
ADCON.5
ADSST
ADCON.3
ADEOC
ADCON.4 ADC
Interrupt
Request
EADC
IEN1.3
CONTROL
+
-
ADDL 2 SAR
ADEN
ADSST
ADEOC
T
SETUP
T
CONV
CLK
T
ADCLK