MCP3204 View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
MCP3204
Microchip Technology
'MCP3204' PDF : 20 Pages View PDF
MCP3204/3208
5.0 SERIAL COMMUNICATIONS
Communication with the MCP3204/3208 devices is
done using a standard SPI-compatible serial interface.
Initiating communication with either device is done by
bringing the CS line low. See Figure 5-1. If the device
was powered up with the CS pin low, it must be brought
high and back low to initiate communication. The first
clock received with CS low and DIN high will constitute
a start bit. The SGL/DIFF bit follows the start bit and will
determine if the conversion will be done using single
ended or differential input mode. The next three bits
(D0, D1 and D2) are used to select the input channel
configuration. Table 5-1 and Table 5-2 show the config-
uration bits for the MCP3204 and MCP3208, respec-
tively. The device will begin to sample the analog input
on the fourth rising edge of the clock after the start bit
has been received. The sample period will end on the
falling edge of the fifth clock following the start bit.
After the D0 bit is input, one more clock is required to
complete the sample and hold period (DIN is a don’t
care for this clock). On the falling edge of the next clock,
the device will output a low null bit. The next 12 clocks
will output the result of the conversion with MSB first as
shown in Figure 5-1. Data is always output from the
device on the falling edge of the clock. If all 12 data bits
have been transmitted and the device continues to
receive clocks while the CS is held low, the device will
output the conversion result LSB first as shown in
Figure 5-2. If more clocks are provided to the device
while CS is still low (after the LSB first data has been
transmitted), the device will clock out zeros indefinitely.
If necessary, it is possible to bring CS low and clock in
leading zeros on the DIN line before the start bit. This is
often done when dealing with microcontroller-based
SPI ports that must send 8 bits at a time. Refer to
Section 6.1 for more details on using the
MCP3204/3208 devices with hardware SPI ports.
CONTROL BIT
SELECTIONS
INPUT
CHANNEL
SINGLE/ D2* D1 D0 CONFIGURATION SELECTION
DIFF
1
X 0 0 single ended
1
X 0 1 single ended
1
X 1 0 single ended
1
X 1 1 single ended
0
X 0 0 differential
0
X 0 1 differential
0
X 1 0 differential
0
X 1 1 differential
*D2 is don’t care for MCP3204
CH0
CH1
CH2
CH3
CH0 = IN+
CH1 = IN-
CH0 = IN-
CH1 = IN+
CH2 = IN+
CH3 = IN-
CH2 = IN-
CH3 = IN+
TABLE 5-1: Configuration Bits for the MCP3204.
CONTROL BIT
SELECTIONS
INPUT
CHANNEL
SINGLE/ D2 D1 D0 CONFIGURATION SELECTION
DIFF
1
0 0 0 single ended CH0
1
0 0 1 single ended CH1
1
0 1 0 single ended CH2
1
0 1 1 single ended CH3
1
1 0 0 single ended CH4
1
1 0 1 single ended CH5
1
1 1 0 single ended CH6
1
1 1 1 single ended CH7
0
0 0 0 differential
CH0 = IN+
CH1 = IN-
0
0 0 1 differential
CH0 = IN-
CH1 = IN+
0
0 1 0 differential
CH2 = IN+
CH3 = IN-
0
0 1 1 differential
CH2 = IN-
CH3 = IN+
0
1 0 0 differential
CH4 = IN+
CH5 = IN-
0
1 0 1 differential
CH4 = IN-
CH5 = IN+
0
1 1 0 differential
CH6 = IN+
CH7 = IN-
0
1 1 1 differential
CH6 = IN-
CH7 = IN+
TABLE 5-2: Configuration Bits for the MCP3208.
DS21298B-page 14
Preliminary
© 1999 Microchip Technology Inc.
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