adc12132 National Semiconductor Corporation, adc12132 Datasheet - Page 30

• 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

www.national.com
Application Information
below is the data bit stream required on DI, during I/O
sequence number 4 in Figure 8, to set CH1 as the positive
input and CH0 as the negative input for the different versions
of ADCs:
Where X can be a logic high (H) or low (L).
1.5 Power Up/Down
The ADC may be powered down by taking the PD pin HIGH
or by the instruction input on DI (see Table 4 and Table 5,
and the Power Up/Down timing diagrams). When the ADC is
1.6 User Mode and Test Mode
An instruction may be issued to the ADC to put it into test
mode, which is used by the manufacturer to verify complete
functionality of the device. During test mode CH0–CH7 be-
come active outputs. If the device is inadvertently put into the
test mode with CS continuously low, the serial communica-
tions may be desynchronized. Synchronization may be re-
gained by cycling the power supply voltage to the device.
Cycling the power supply voltage will also set the device into
user mode. If CS is used in the serial interface, the ADC may
be queried to see what mode it is in. This is done by issuing
a “read STATUS register” instruction to the ADC. When bit 9
of the status register is high, the ADC is in test mode; when
bit 9 is low the ADC, is in user mode. As an alternative to
cycling the power supply, an instruction sequence may be
used to return the device to user mode. This instruction
sequence must be issued to the ADC using CS. The follow-
ing table lists the instructions required to return the device to
user mode. Note that this entire sequence, including both
Test Mode and User Mode values, should be sent to recover
from the test mode.
ADC12132 *
* ADC12132 is obsolete; shown for reference only.
ADC12130
ADC12138
Number
Part
and
DI0 DI1 DI2 DI3 DI4 DI5 DI6 DI7
L
L
H
H
L
L
FIGURE 8. Changing the ADC’s Conversion Configuration
DI Data
L
L
H
L
(Continued)
L
L
H
X
X
L
30
powered down in this way, the A/D conversion circuitry is
deactivated but the digital I/O circuitry is kept active. Hard-
ware power up/down is controlled by the state of the PD pin.
Software power-up/down is controlled by the instruction is-
sued to the ADC. If a software power up instruction is issued
to the ADC while a hardware power down is in effect (PD pin
high) the device will remain in the power-down state. If a
software power down instruction is issued to the ADC while
a hardware power up is in effect (PD pin low), the device will
power down. When the device is powered down by software,
it may be powered up by either issuing a software power up
instruction or by taking PD pin high and then low. If the power
down command is issued during an A/D conversion, that
conversion is interrupted, so the data output after power up
cannot be relied upon.
X = Don’t Care
The power up, data with or without sign, and acquisition time
instructions should be resent after returning to the user
mode. This is to ensure that the ADC is in the required state
before a conversion is started.
USER MODE
TEST MODE
Set DO with
Instruction
Instructions
Conversion
Acquisition
Test Mode
Power Up
or without
Start a
Reset
Time
Sign
Set
or L
or L
or L
DI0 DI1 DI2 DI3 DI4 DI5 DI6 DI7
H
H
H
H
L
L
L
L
L
or L
or L
X
H
H
L
L
L
L
L
L
or L
H
X
L
L
L
L
L
L
L
or L
DI Data
X
H
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
L
or L
01207933
H
H
H
H
H
H
L
L
L
or L
H
H
H
H
H
H
H
H
L
or L
H
H
H
H
H
L
L
L
L