AD7863ARS-10REEL datasheet(18/24 Pages) AD

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AD7863

Rev. B | Page 18 of 24

ADDRESS

DECODE

ADDRESS BUS

BUSY

DB13

DB0

DATA BUS

AD7863*

*ADDITIONAL PINS OMITTED FOR CLARITY.

OPTIONAL

CONVST

TMS320C25

A15

INTn

STRB

R/W

DMD15

DMD0

READY

MSC

Figure 21. AD7863 to TMS320C25 Interface

Some applications may require that the conversion be initiated

by the microprocessor rather than an external timer. One

option is to decode the AD7863 CONVST from the address bus

so that a write operation starts a conversion. Data is read at the

end of the conversion sequence as before. Figure 23 shows an

example of initiating conversion using this method. Note that

for all interfaces, it is preferred that a read operation not be

attempted during conversion.

AD7863 TO MC68000 INTERFACE

An interface between the AD7863 and the MC68000 is shown

in Figure 22. As before, conversion can be supplied from the

MC68000 or from an external source. The AD7863 BUSY line

can be used to interrupt the processor or, alternatively, software

delays can ensure that conversion has been completed before a

read to the AD7863 is attempted. Because of the nature of its

interrupts, the MC68000 requires additional logic (not shown

in Figure 23) to allow it to be interrupted correctly. For further

information on MC68000 interrupts, consult the MC68000

users manual.

The MC68000 AS and R/W outputs are used to generate a

separate RD input signal for the AD7863. CS is used to drive

the MC68000 DTACK input to allow the processor to execute

a normal read operation to the AD7863. The conversion results

are read using the following MC68000 instruction:

MOVE.W ADC, D0

where:

D0 is the 68000 D0 register.

ADC is the AD7863 address.

ADDRESS

DECODE

ADDRESS BUS

A15

DTACK

D15

DB13

DB0

DATA BUS

MC68000

AD7863*

*ADDITIONAL PINS OMITTED FOR CLARITY.

OPTIONAL

CONVST

R/W

Figure 22. AD7863 to MC68000 Interface

AD7863 TO 80C196 INTERFACE

Figure 23 shows an interface between the AD7863 and the

80C196 microprocessor. Here, the microprocessor initiates

conversion. This is achieved by gating the 80C196 WR signal

with a decoded address output (different from the AD7863 CS

address). The AD7863 BUSY line is used to interrupt the

microprocessor when the conversion sequence is completed.

ADDRESS

DECODE

ADDRESS BUS

A15

D15

BUSY

DB13

DB0

DATA BUS

80C196

AD7863*

*ADDITIONAL PINS OMITTED FOR CLARITY.

Figure 23. AD7863–80C196 Interface

VECTOR MOTOR CONTROL

The current drawn by a motor can be split into two components:

one produces torque and the other produces magnetic flux.

For optimal performance of the motor, these two components

should be controlled independently. In conventional methods of

controlling a three-phase motor, the current (or voltage)

supplied to the motor and the frequency of the drive are the

basic control variables. However, both the torque and flux are

functions of current (or voltage) and frequency. This coupling

effect can reduce the performance of the motor because, for

example, if the torque is increased by increasing the frequency,

the flux tends to decrease.

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