AD7863
Rev. B | Page 17 of 24
MICROPROCESSOR INTERFACING
The AD7863 high speed bus timing allows direct interfacing to
DSP processors as well as modern 16-bit microprocessors.
Suitable microprocessor interfaces are shown in
Figure 19
through
Figure 23.
AD7863 TO ADSP-2100 INTERFACE
Figure 19 shows an interface between the AD7863 and the
ADSP-2100. The
CONVST
signal can be supplied from the
ADSP-2100 or from an external source. The AD7863 BUSY line
provides an interrupt to the ADSP-2100 when conversion is
completed on both channels. The two conversion results can
then be read from the AD7863 using two successive reads to the
same memory address. The following instruction reads one of
the two results:
MR0 = DM (ADC)
where:
MR0 is the ADSP-2100 MR0 register.
ADC is the AD7863 address.
ADDR
DECODE
EN
ADDRESS BUS
DMA13
DMA0
DMS
IRQn
DMRD (RD)
DMD15
DMD0
CS
A0
BUSY
RD
DB13
DB0
DATA BUS
ADSP-2100
(ADSP-2101/
ADSP-2102)
AD7863*
*ADDITIONAL PINS OMITTED FOR CLARITY.
OPTIONAL
CONVST
06411-019
Figure 19. AD7863 to ADSP-2100 Interface
AD7863 TO ADSP-2101/ADSP-2102 INTERFACE
The interface outlined in Figure 19 also forms the basis for an
interface between the AD7863 and the ADSP-2101/ADSP-2102.
The READ line of the ADSP-2101/ADSP-2102 is labeled
RD
. In
this interface, the
RD
pulse width of the processor can be
programmed using the data memory wait state control register.
The instruction used to read one of the two results is as outlined
for the ADSP-2100.
AD7863 TO TMS32010 INTERFACE
An interface between the AD7863 and the TMS32010 is shown
in
Figure 20. Once again the
CONVST
signal can be supplied
from the TMS32010 or from an external source, and the
TMS32010 is interrupted when both conversions have been
completed. The following instruction is used to read the
conversion results from the AD7863:
IN D, ADC
where:
D is data memory address.
ADC is the AD7863 address.
ADDRESS
DECODE
EN
ADDRESS BUS
PA2
PA0
MEN
INT
DEN
D15
D0
CS
A0
BUSY
RD
DB13
DB0
DATA BUS
TMS32010
AD7863*
*ADDITIONAL PINS OMITTED FOR CLARITY.
OPTIONAL
CONVST
6411-020
Figure 20. AD7863 to TMS32010 Interface
AD7863 TO TMS320C25 INTERFACE
Figure 21 shows an interface between the AD7863 and the
TMS320C25. As with the two previous interfaces, conversion
can be initiated from the TMS320C25 or from an external
source, and the processor is interrupted when the conversion
sequence is completed. The TMS320C25 does not have a
separate
RD
output to drive the AD7863
RD
input directly. This
has to be generated from the processor
STRB
and R/
W
outputs
with the addition of some logic gates. The
RD
signal is OR
gated with the
MSC
signal to provide the one WAIT state
required in the read cycle for correct interface timing.
Conversion results are read from the AD7863 using the
following instruction:
IN D, ADC
where:
D is data memory address.
ADC is the AD7863 address.
