Microchip Technology MCP3422, Руководство пользователя

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MCP3422/3/4
DS22088B-page 32
©
2008 Microchip Technology Inc.
6.1.4 DEVICE CONNECTION TEST
The user can test the presence of the MCP3422/3/4 on
the I
2
C bus line without performing an input data con-
version. This test can be achieved by checking an
acknowledge response from the MCP3422/3/4 after
sending a read or write command. Here is an example
using
Figure 6-3 :
a. Set the R/W bit “HIGH” in the address byte.
b. Check the ACK pulse after sending the
address byte.
If the device acknowledges (ACK =
0
), then the
device is connected, otherwise it is not
connected.
c. Send STOP or START bit.
FIGURE 6-3: I
2
C Bus Connection Test.
6.1.5 DIFFERENTIAL AND
SINGLE-ENDED CONFIGURATION
Figure 6-4 shows typical connection examples for dif-
ferential and single-ended inputs. Differential input sig-
nals can be connected to the CHn+ and CHn- input
pins, where n = the channel number (1, 2, 3, or 4). For
the single-ended input, the input signal is applied to one
of the input pins (typically connected to the CHn+ pin)
while the other input pin (typically CHn- pin) is
grounded. All device characteristics hold for the
single-ended configuration, but this configuration loses
one bit resolution because the input can only stand in
positive half scale. Refer to
Section 1.0 “Electrical
Characteristics” .
FIGURE 6-4: Differential and
Single-Ended Input Connections.
1 2 3 4 5 6 7 8 9 SCL
SDA
1
1
0 1 A2 A1 A0 1
Start
Bit
Address Byte
Address bits
Device bits
R/W
Stop
Bit
MCP342x
ACK
Response
(a) Differential Input Signal Connection:
CHn+
CHn-
MCP342x
Input Signal
(b) Single-ended Input Signal Connection:
CHn+
CHn-
MCP342x
Input Signal
Sensor
Sensor
Excitation
Excitation
R
1
R
2