SPI Communications
Atlas® Digital Amplifier Complete Technical Reference
89
5
5.4
Sending an Amplifier Disable
Figure 5-3:
Amplifier
Disable
Command
Format
The header can be used to rapidly disable Atlas motor output. This operation is identical to sending a
SetOperationMode
command with current loop and power stage modules disabled, however faster.
To disable Atlas output, a 1 should appear in the ‘x’ field (bit 15 of the first header word), the high four bits of Data
1 should be loaded with a 1, a checksum should be loaded into the low 8 bits of Data 1, and 0 should be loaded into
Data 2. This is shown in
The checksum byte should be loaded such that when the ones-complement checksum of all four bytes of the header
words, the byte value 0xFF, and the transmitted checksum byte evaluate to 0xFF. If the checksum is not correct, Atlas
will take no action as a result of this packet transmission.
5.5
Sending a NOP
Figure 5-4:
NOP Command
Format
There are times when it may be useful to send a header without providing a new torque command or disabling the
drive. This might be the case, for example, when the external controller only wants to update the ‘t’ (trace) header field
or the ‘u’ (update) fields. In addition, this may be useful to verify controller to Atlas communication without requesting
a specific action.
Such an operation is called a NOP (no operation) header transaction.
To send a NOP to Atlas, a 1 should appear in the ‘x’ field (bit 15 of the first header word), the high four bits of Data
1 should be loaded with a 0, the low byte of Data 1 can contain anything, and Data 2 can contain anything. This is
shown in
.
Controller word 0
1
t
u
0
1
checksum
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
0
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 0
1
t
u
0
0
anything
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
anything
Atlas word 1
Atlas checksum
Controller checksum
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
