Z-World RabbitCore, Руководство пользователя

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User’s Manual 75
B.4.2 Analog Features
The RCM3600 Prototyping Board has an onboard ADS7870 A/D converter to demon-
strate the interface capabilities of the Rabbit 3000. The A/D converter multiplexes con-
verted signals from eight single-ended or three differential inputs to alternate Serial Port B
on the Rabbit 3000 (Parallel Port pins PD4 and PD5).
B.4.2.1 A/D Converter Inputs
Figure B-5 shows a pair of A/D converter input circuits. The resistors form an approxi-
mately 10:1 attenuator, and the capacitor filters noise pulses from the A/D converter input.
Figure B-5. A/D Converter Inputs
The A/D converter chip can make either single-ended or differential measurements
depending on the value of the
opmode
parameter in the software function call. Adjacent
A/D converter inputs can be paired to make differential measurements. The default setup
on the Prototyping Board is to measure only positive voltages for the ranges listed in
Table B-2.
178 k W
ADC_IN0
AGND
+ V
ADC_IN1
VREF
178 k W
1 nF
20 k
W
ADC
20 k
W
1 nF
User Circuits
JP7