9

SA828

Fig. 17 Typical SA828 programming routine

WRITE R1

WRITE R2

WRITE R4

POWER ON

WRITE R0

RST

↓ 0

RST

↑ 1

CHANGE

CONTROL

DATA ?

CHANGE

INITIALISATION

DATA ?

YES

NO

YES

NO

WRITE R1

WRITE R2

WRITE R3

WRITE R0

WRITE R1

WRITE R2

WRITE R3

WRITE R0

WRITE

INITIALISATION

DATA

WRITE TO CONTROL

REGISTER INHIBITING

PWM OUTPUTS

BEFORE COMPLETING

RESET CYCLE

ENABLE

PWM OUTPUTS

WRITE

CONTROL

DATA























































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,

accuracy (i.e 4096 equal steps) from 0Hz to

in the initialisation register. In this case, with

the power frequency can be adjusted in increments of 0·06Hz.

We can only have

pfs as an integer, so if we assign pfs =

1638 this gives

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

100

0

1

1

0

0

0

1

1

Temporary Register R0

0

0

1

X

0

1

1

0

Temporary Register R1

1

1

0

0

Temporary Register R2

1100

F/R

OM

INH

X

Fig. 16

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.

80 x 255

100

⇒ A =

=

= 204

4096

⇒ pfs =

=

= 1638·4

100 x 4096

250

A

225

x

pfs