ADUC842 Analog Devices, ADUC842 Datasheet - Page 23

• Manufacturer Part Number: ADUC842
• Description: Precision Analog Microcontroller: 16MIPS 8052 Flash MCU + 8-Ch 12-Bit ADC + Dual 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC842

• Mcu Core: 8052
• Mcu Speed (mips): 16
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 8
• Other: PWM

ADC CIRCUIT INFORMATION
General Overview
The ADC conversion block incorporates a fast, 8-channel,
12-bit, single-supply ADC. This block provides the user with
multichannel mux, track-and-hold, on-chip reference, calibra-
tion features, and ADC. All components in this block are easily
configured via a 3-register SFR interface.
The ADC converter consists of a conventional successive
approximation converter based around a capacitor DAC. The
converter accepts an analog input range of 0 V to V
precision, 15 ppm, low drift, factory calibrated 2.5 V reference is
provided on-chip. An external reference can be connected as
described in the Voltage Reference Connections section. This
external reference can be in the range 1 V to AV
Single-step or continuous conversion modes can be initiated in
software or alternatively by applying a convert signal to an
external pin. Timer 2 can also be configured to generate a
repetitive trigger for ADC conversions. The ADC may be
configured to operate in a DMA mode whereby the ADC block
continuously converts and captures samples to an external
RAM space without any interaction from the MCU core. This
automatic capture facility can extend through a 16 MByte
external data memory space.
The ADuC841/ADuC842/ADuC843 are shipped with factory
programmed calibration coefficients that are automatically
downloaded to the ADC on power-up, ensuring optimum ADC
performance. The ADC core contains internal offset and gain
calibration registers that can be hardware calibrated to
minimize system errors.
A voltage output from an on-chip band gap reference propor-
tional to absolute temperature can also be routed through the
front end ADC multiplexer (effectively a 9th ADC channel
input), facilitating a temperature sensor implementation.
DD
.
REF
. A high
Rev. 0 | Page 23 of 88
ADC Transfer Function
The analog input range for the ADC is 0 V to V
range, the designed code transitions occur midway between
successive integer LSB values, i.e., 0.5 LSB, 1.5 LSB, 2.5 LSB . . .
FS –1.5 LSB. The output coding is straight binary with 1 LSB =
FS/4096 or 2.5 V/4096 = 0.61 mV when V
input/output transfer characteristic for the 0 V to V
shown in Figure 28.
Typical Operation
Once configured via the ADCCON 1–3 SFRs, the ADC converts
the analog input and provides an ADC 12-bit result word in the
ADCDATAH/L SFRs. The top 4 bits of the ADCDATAH SFR
are written with the channel selection bits to identify the channel
result. The format of the ADC 12-bit result word is shown in
Figure 29.
TOP 4 BITS
CH–ID
111...101
000...010
111...111
111...110
111...100
000...011
000...001
000...000
OUTPUT
CODE
0V 1LSB
Figure 29. ADC Result Word Format
Figure 28. ADC Transfer Function
1LSB =
ADuC841/ADuC842/ADuC843
4096
FS
LOW 8 BITS OF THE
ADC RESULT WORD
HIGH 4 BITS OF
ADC RESULT WORD
REF
= 2.5 V. The ideal
+FS
ADCDATAH SFR
ADCDATAL SFR
REF
. For this
REF
range is