adc12132 National Semiconductor Corporation, adc12132 Datasheet - Page 37

• Manufacturer Part Number: adc12132
• Description: Self-calibrating 12-bit Plus Sign Serial I/o A/d Converters With Mux And Sample/hold
• Manufacturer: National Semiconductor Corporation

Application Information
Note: V
caps.
The assignment of the RS232 port is shown below
A sample program, written in Microsoft QuickBasic, is shown
on the next page. The program prompts for data mode select
instruction to be sent to the A/D. This can be found from the
Mode Programming table shown earlier. The data should be
entered in “1”s and “0”s as shown in the table with DI0 first.
Next, the program prompts for the number of SCLKs re-
quired for the programmed mode select instruction. For in-
stance, to send all “0”s to the A/D, selects CH0 as the +input,
CH1 as the −input, 12-bit conversion, and 13-bit MSB first
data output format (if the sign bit was not turned off by a
previous instruction). This would require 13 SCLK periods
since the output data format is 13 bits.
The ADC powers up with No Auto Cal, No Auto Zero, 10
CCLK Acquisition Time, 12-bit conversion, data out with
A
+
, V
D
+
, and V
REF
COM1
+
on the ADC12138 each have 0.01 µF and 0.1 µF chip caps, and 10 µF tantalum caps. All logic devices are bypassed with 0.1 µF
Input Address
Output Address
(Continued)
3FE
3FC
B7
X
X
B6
37
X
X
sign, power up, 12- or 13-bit MSB First, and user mode. Auto
Cal, Auto Zero, Power Up and Power Down instructions do
not change these default settings. The following power up
sequence should be followed:
1. Run the program
2. Prior to responding to the prompt apply the power to the
3. Respond to the program prompts
It is recommended that the first instruction issued to the
ADC12138 be Auto Cal (see Section 1.1).
B5
X
X
ADC12138
CTS
B4
0
B3
X
X
B2
X
X
RTS
B1
X
DTR
B0
X
01207946
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