MCP3208-CI/SN Microchip Technology, MCP3208-CI/SN Datasheet - Page 15

• Manufacturer Part Number: MCP3208-CI/SN
• Description: 2.7V 4-Channel/8-Channel 10-Bit A/D Converters with SPI Serial Interface
• Manufacturer: Microchip Technology

5.0
Communication with the MCP3204/3208 devices is
accomplished 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 D
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 configuration bits for the MCP3204 and MCP3208,
respectively. The device will begin to sample the ana-
log 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.
Once the D0 bit is input, one more clock is required to
complete the sample and hold period (D
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 D
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.
2002 Microchip Technology Inc.
SERIAL COMMUNICATIONS
IN
line before the start bit. This is
IN
IN
is a “don’t
high will
TABLE 5-1:
TABLE 5-2:
* D2 is a “don’t care” for MCP3204
Single/
Single
/Diff
Diff
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
Control Bit
Control Bit
Selections
Selections
D2* D1 D0
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
X
X
X
X
X
X
X
X
D1 D0
MCP3204/3208
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
CONFIGURATION BITS FOR
THE MCP3204
CONFIGURATION BITS FOR
THE MCP3208
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Configuration
Configuration
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
single-ended
differential
differential
differential
differential
differential
differential
differential
differential
differential
differential
differential
differential
Input
Input
DS21298C-page 15
CH0 = IN+
CH1 = IN+
CH2 = IN+
CH3 = IN+
CH0 = IN+
CH1 = IN+
CH2 = IN+
CH3 = IN+
CH4 = IN+
CH5 = IN+
CH6 = IN+
CH7 = IN+
Selection
CH1 = IN-
CH0 = IN-
CH3 = IN-
CH2 = IN-
Selection
CH1 = IN-
CH0 = IN-
CH3 = IN-
CH2 = IN-
CH5 = IN-
CH4 = IN-
CH7 = IN-
CH6 = IN-
Channel
Channel
CH0
CH1
CH2
CH3
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7