Atlas® Digital Amplifier Complete Technical Reference
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5
5.SPI Communications
In This Chapter
SPI Communications Overview
Packet Header
Sending a Voltage or Torque Output Value
Sending an Amplifier Disable
Sending aNOP
Sending Atlas Commands
5.1
SPI Communications Overview
Atlas uses an SPI (Serial Peripheral Interface) digital connection to communication with the external controller. This
connection is used to setup Atlas parameters, specify voltage or torque output values, monitor Atlas operation, as well
as other functions.
SPI is a convenient interface because it is available on many microprocessors, provides relatively high speed
communications, and uses only 4 signals; SPIClk (Clock), SPICS (chip select), SPISI (slave in), and SPISO (slave out).
Atlas utilizes standard SPI signaling and timing control for the hardware interface and implements a higher level protocol
on top of this. See
Section 3.6, “AC Characteristics”
to learn more about low-level hardware SPI signal timing, voltage
levels, etc.
Figure 5-1:
SPI
Communica-
tions Protocol
Overview
All communications to and from Atlas are in the form of a packet.
shows the overall packet format. A falling
edge of the chip select begins the packet, and a rising edge of the chip select ends the packet. All Atlas SPI packets are
comprised of a two word header and one or more optional command words.
Controller word 0
x
t
u
0
Header data 1
Atlas word 0
SPI Status word
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Controller word 1
Header data 2
Atlas word 1
Atlas checksum
Controller checksum
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Controller word 2-N
Optional command
Atlas word 2-N
Optional command response
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
