MCP3302-XI/SL Microchip Technology, MCP3302-XI/SL Datasheet - Page 25

• Manufacturer Part Number: MCP3302-XI/SL
• Description: 13-Bit Differential Input, Low Power A/D Converter with SPI Serial Interface, -40C to +85C, 14-SOIC 150mil, TUBE
• Manufacturer: Microchip Technology

7.3
With most microcontroller SPI ports, it is required to
send groups of eight bits. It is also required that the
microcontroller SPI port be configured to clock out data
on the falling edge of clock and latch data in on the
rising
MCP3302 and MCP3304 devices may not need
multiples of eight clocks, it will be necessary to provide
more clocks than are required. This is usually done by
sending ‘leading zeros’ before the start bit. For
example,
MCP3302/04 devices can be interfaced to a MCU with
a hardware SPI port.
shown in SPI Mode 0,0, which requires that the SCLK
from the MCU idles in the ‘low’ state, while
shows the similar case of SPI Mode 1,1, where the
clock idles in the ‘high’ state.
As shown in
A/D Converter contains 6 leading zeros before the start
bit. Arranging the leading zeros this way produces the
13 data bits to fall in positions easily manipulated by the
MCU. The sign bit is clocked out of the A/D Converter
on the falling edge of clock number 11, followed by the
remaining data bits (MSB first). After the second eight
clocks have been sent to the device, the MCU receive
buffer will contain 2 unknown bits (the output is at high
impedance for the first two clocks), the null bit, the sign
bit, and the 4 highest order bits of the conversion. After
the third byte has been sent to the device, the receive
register will contain the lowest order eight bits of the
conversion
converted data can be obtained by using this method.
Figure 7-5
which requires that the clock idles in the high state. As
with mode 0,0, the A/D Converter outputs data on the
falling edge of the clock and the MCU latches data from
the A/D Converter in on the rising edge of the clock.
© 2007 Microchip Technology Inc.
edge.
Using the MCP3302/04 with
Microcontroller (MCU) SPI Ports
Figure 7-4
shows the same situation in SPI Mode 1,1,
Figure
results.
Because
7-4, the first byte transmitted to the
Figure 7-4
and
Easier manipulation
communication
Figure 7-5
depicts the operation
show how the
Figure 7-5
with
of
the
the
MCP3302/04
DS21697D-page 25