SA828
Control Register Programming Example
The control register would normally be updated many times
while the motor is running, but just one example is given here.
It is assumed that the initialisation register has already heen
programmed with the parameters given in the previous example.
A power waveform of 100Hz is required with a PWM
waveform amplitude of 80% of that stored in the ROM. The
phase sequence should be set to give forward motor rotation.The
outputs should be enabled and no overmodulation is required.
POWER ON
RST
↓
0
1. Setting the power frequency
The power frequency,
f
POWER
, can be selected to 12-bit
accuracy (i.e 4096 equal steps) from 0Hz to
f
RANGE
as defined
in the initialisation register. In this case, with
f
RANGE
= 250Hz,
the power frequency can be adjusted in increments of 0·06Hz.
f
f
POWER
=
RANGE
x
pfs
4096
f
x 4096
100 x 4096
⇒
pfs
=
POWER
=
=
1638·4
f
RANGE
250
We can only have
pfs
as an integer, so if we assign
pfs
=
1638 this gives
f
POWER
= 99.97 Hz.The 12-bit binary equivalent
of this value gives a PFS word of 011001100110 in temporary
registers R0 and R1.
2. Setting overmodulation, forward/reverse, output inhibit
Overmodulation is not required therefore OM = 0.
Forward motor control is required (i.e., the phase sequence
of the PWM outputs should be red-yellow-blue) therefore forward/
reverse bit F/R = 0.
Output inhibit should be inactive (i e., the outputs should be
active), therefore INH= 1.
These bits are all set in temporary register R1.
3. Setting the power waveform amplitude
A
A
POWER
=
x 100%
225
A
x 255
80 x 255
⇒
A
=
POWER
=
=
204
100
100
The 8-bit binary equivalent of this value gives an AMP word
of 11001100 in temporary register R2. The data which must be
programmed into the three temporary registers R0, R1 and R2
(for transfer into the control register) in order to achieve the
parameters in the example given, is shown in Fig. 16.
WRITE
INITIALISATION
DATA
WRITE R0
WRITE R1
WRITE R2
WRITE R4
WRITE R0
WRITE R1
WRITE R2
WRITE R3
WRITE TO CONTROL
REGISTER INHIBITING
PWM OUTPUTS
BEFORE COMPLETING
RESET CYCLE
ENABLE
PWM OUTPUTS
RST
↑
1
WRITE
CONTROL
DATA
WRITE R0
WRITE R1
WRITE R2
WRITE R3
Temporary Register R0
0
1
1
0
0
0
1
1
CHANGE
CONTROL
DATA ?
NO
YES
PFS
7
PFS
6
PFS
5
PFS
4
PFS
3
PFS
2
PFS
1
PFS
0
Temporary Register R1
0
F/R
0
OM
1
INH
X
X
0
1
1
0
NO
PFS
11
PFS
10
PFS
9
PFS
8
CHANGE
INITIALISATION
DATA ?
YES
Temporary Register R2
1
1
0
0
1
1
0
0
AMP
7
AMP
6
AMP
5
AMP
4
AMP
3
AMP
2
AMP
1
AMP
0
Fig. 16
Fig. 17 Typical SA828 programming routine
9
MITEL [ MITEL NETWORKS CORPORATION ]
