MCP3021 Microchip Technology, Inc., MCP3021 Datasheet - Page 17

• Manufacturer Part Number: MCP3021
• Description: The Microchip Technology Inc
• Manufacturer: Microchip Technology, Inc.

The input signal will initially be sampled with the first
falling edge of the clock following the transmission of a
logic-high R/W bit. Additionally, with the rising edge of
the SCL, the ADC will transmit an acknowledge bit
(ACK = 0). The master must release the data bus dur-
ing this clock pulse to allow the MCP3021 to pull the
line low (refer to Figure 5-3).
For consecutive samples, sampling begins on the last
bit of the lower data byte. Refer to Figure 5-6 for timing
diagram.
FIGURE 5-5:
5.3.3
For consecutive samples, sampling begins on the fall-
ing edge of the last bit of the lower data byte. See
Figure 5-6 for timing.
FIGURE 5-6:
2003 Microchip Technology Inc.
SDA
SCL
SDA
SCL
CONSECUTIVE CONVERSIONS
S
T
A
R
T
S
Device bits
S
T
A
R
T
S
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
1 0 0 1 A
Device bits
t
initiated here
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1 0 0 1 A2 A1 A0
ACQ
t
initiated here
ACQ
Executing a Conversion.
Continuous Conversion.
Address Byte
+ t
Address Byte
+ t
CONV
CONV
Address bits
2
Address bits
is
A
1
is
A
0
W
R
/
W
R
/
A
C
K
A
C
K
0 0 0 0 D D D
0 0 0 0 D D D
Upper Data Byte
Upper Data Byte (n)
f
SAMP
9 8
= 22.3 ksps (f
9 8 7
5.3.2
After the MCP3021 acknowledges the address byte,
the device will transmit four ‘0’ bits followed by the
upper four data bits of the conversion. The master
device will then acknowledge this byte with an
ACK = low. With the following six clock pulses, the
MCP3021 will transmit the lower six data bits from the
conversion. The last two bits are “don’t cares”, and do
not contain valid data. The master then sends an
ACK = high, indicating to the MCP3021 that no more
data is requested. The master can then send a stop bit
to end the transmission.
7
D
6
D
6
A
C
K
READING THE CONVERSION DATA
A
C
K
CLK
D
5
D
5
= 400 kHz)
D
4
t
initiated here
Lower Data Byte
ACQ
Lower Data Byte (n)
D
4
D
3
21 22 23 24 25 26 27
D
3
+ t
D
2
CONV
D
2
D
1
D
1
MCP3021
D
0 X X
is
D
0 X X
DS21805A-page 17
N
A
K
A
C
K
O
P
S
T
P
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