SA8281/IG/DP1S Ver la hoja de datos (PDF) - Mitel Networks
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SA8281/IG/DP1S Datasheet PDF : 14 Pages
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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.
1. Setting the power frequency
The power frequency, fPOWER, can be selected to 12-bit
accuracy (i.e 4096 equal steps) from 0Hz to fRANGE as defined
in the initialisation register. In this case, with fRANGE = 250Hz,
the power frequency can be adjusted in increments of 0·06Hz.
fPOWER = fRANGE x pfs
4096
⇒ pfs = fPOWER x 4096 = 100 x 4096 = 1638·4
fRANGE
250
We can only have pfs as an integer, so if we assign pfs =
1638 this gives fPOWER = 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
APOWER
=
x
225
100%
⇒ A = APOWER x 255 = 80 x 255 = 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.
Temporary Register R0
01100011
PFS7 PFS6 PFS5 PFS4 PFS3 PFS2 PFS1 PFS0
Temporary Register R1
001X0110
F/R OM INH X PFS11 PFS10 PFS9 PFS8
Temporary Register R2
11001100
AMP7 AMP6 AMP5 AMP4 AMP3 AMP2 AMP1 AMP0
Fig. 16
SA828
POWER ON
WRITE
INITIALISATION
DATA
WRITE TO CONTROL
REGISTER INHIBITING
PWM OUTPUTS
BEFORE COMPLETING
RESET CYCLE
ENABLE
PWM OUTPUTS
RST ↓ 0
WRITE R0
WRITE R1
WRITE R2
WRITE R4
WRITE R0
WRITE R1
WRITE R2
WRITE R3
RST ↑ 1
WRITE
CONTROL
DATA
WRITE R0
WRITE R1
WRITE R2
WRITE R3
CHANGE YES
CONTROL
DATA ?
NO
NO
CHANGE
INITIALISATION
DATA ?
YES
Fig. 17 Typical SA828 programming routine
9
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