AD7891BS-1 Analog Devices Inc, AD7891BS-1 Datasheet - Page 16

• Manufacturer Part Number: AD7891BS-1
• Description: IC DAS 12BIT 8CH 44-MQFP
• Manufacturer: Analog Devices Inc
• Type: Data Acquisition System (DAS)r

Specifications of AD7891BS-1

• Rohs Status: RoHS non-compliant
• Resolution (bits): 12 b
• Sampling Rate (per Second): 500k
• Data Interface: Serial, Parallel
• Voltage Supply Source: Single Supply
• Voltage - Supply: 5V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 44-MQFP, 44-PQFP

AD7891
PARALLEL INTERFACING
The parallel port on the AD7891 allows the device to be interfaced
to microprocessors or DSP processors as a memory mapped
or I/O mapped device. The CS and RD inputs are common to
all memory peripheral interfacing. Typical interfaces to different
processors are shown in Figures 12 to 15. In all the interfaces
shown, an external timer controls the CONVST input of the
AD7891 and the EOC output interrupts the host DSP.
AD7891 to ADSP-21xx
Figure 12 shows the AD7891 interfaced to the ADSP-21xx
series of DSPs as a memory mapped device. A single wait state
may be necessary to interface the AD7891 to the ADSP-21xx
depending on the clock speed of the DSP. This wait state can
be programmed via the data memory wait state control register
of the ADSP-21xx (please see the ADSP-2100 family Users
Manual for details). The following instruction reads data
from the AD7891.
where ADC is the address of the AD7891.
AD7891 to TMS32020, TMS320C25, and TMS320C5x
Parallel interfaces between the AD7891 and the TMS32020,
TMS320C25, and TMS320C5x family of DSPs are shown in
Figure 13. The memory mapped address chosen for the
AD7891 should be chosen to fall in the I/O memory space of
the DSPs.
Figure 13. AD7891 to TMS32020/TMS320C25/TMS320C5x
Parallel Interface
Figure 12. AD7891 to ADSP-21xx Parallel Interface
*ADDITIONAL PINS OMITTED FOR CLARITY
*ADDITIONAL PINS OMITTED FOR CLARITY
TMS32020/
TMS320C25/
TMS320C5x*
ADSP-21xx*
A13 TO A0
D23 TO D8
A15 TO A0
D23 TO D0
READY
STRB
IRQ2
DMS
INTx
MSC
R/W
WR
RD
IS
MR = DM (ADC)
ADDRESS BUS
ADDRESS BUS
EN
EN
DATA BUS
DATA BUS
DECODE
DECODE
ADDR
ADDR
TMS320C25
ONLY
DB11 TO DB0
RD
CS
WR
RD
EOC
CS
WR
EOC
DB11 TO DB0
AD7891*
AD7891*
–16–
The parallel interface on the AD7891 is fast enough to interface
to the TMS32020 with no extra wait states. If high speed glue
logic, such as 74AS devices, are used to drive the WR and RD
lines when interfacing to the TMS320C25, then again no wait
states are necessary. However, if slower logic is used, data accesses
may be slowed sufficiently when reading from and writing to the
part to require the insertion of one wait state. In such a case,
this wait state can be generated using the single OR gate to
combine the CS and MSC signals to drive the READY line of
the TMS320C25, as shown in Figure 13. Extra wait states are
necessary when using the TMS320C5x at their fastest clock
speeds. Wait states can be programmed via the IOWSR and
CWSR registers (see the TMS320C5x User Guide for details).
Data is read from the ADC using the following instruction:
where D is the memory location where the data is to be stored,
and ADC is the I/O address of the AD7891.
AD7891 to TMS320C3x
Figure 14 shows a parallel interface between the AD7891 and
the TMS320C3x family of DSPs. The AD7891 is interfaced to
the expansion bus of the TMS320C3x. A single wait state is
required in this interface. This can be programmed using the
WTCNT bits of the expansion bus control register (see the
TMS320C3x Users Guide for details). Data from the AD7891
can be read using the following instruction:
where ARn is an auxiliary register containing the lower 16 bits
of the address of the AD7891 in the TMS320C3x memory
space, and Rx is the register into which the ADC data is loaded.
Figure 14. AD7891 to TMS320C3x Parallel Interface
*ADDITIONAL PINS OMITTED FOR CLARITY
TMS320C3x*
XD23 TO XD0
XA15 TO XA0
IOSTRB
XR/W
INTx
EXPANSION DATA BUS
LDI
ADDRESS BUS
IN D, ADC
DECODE
¥
ADDR
ARn Rx
,
RD
CS
WR
EOC
DB11 TO DB0
AD7891*
REV. D