LTC1272-3ACS View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1272-3ACS' PDF : 20 Pages View PDF
LTC1272
APPLICATI S I FOR ATIO
HBEN
t8
t9
t8
t9
t8
t9
CS
t1
t4
t5
RD
t2
tCONV
t1
t4
t5
t1
t4
t5
t10
t11
t2
BUSY
DATA
HOLD
t3
t7
OLD DATA
DB7-DB0
t12
t3
t7
NEW DATA
DB11-DB8
t3
t7
NEW DATA
DB7-DB0
t12
TRACK
Figure 17. ROM Mode, Two Byte Read Timing Diagram
Table 5. ROM Mode, Two Byte Read Data Bus Status
Data Outputs
D7
D6
D5
D4
D3/11
D2/10
First Read
DB7
DB6
DB5
DB4
DB3
DB2
Second Read
Low
Low
Low
Low
DB11
DB10
Third Read
DB7
DB6
DB5
DB4
DB3
DB2
LTC1272 • TA19
D1/9
D0/8
DB1
DB0
DB9
DB8
DB1
DB0
ROM Mode, Two Byte READ
As previously mentioned for a two byte read, only data
outputs D7 . . . D0/8 are used. Conversion is started in the
normal way with a Read operation and the data output
status is the same as the ROM Mode, Parallel Read. See
Figure 17 timing diagram and Table 5 data bus status. Two
more Read operations are required to access the new
conversion result. A delay equal to the LTC1272 conver-
sion time must be allowed between conversion start and
the second data Read operation. The second Read opera-
tion, with HBEN high, disables conversion start and places
the high byte (4 MSBs) on data outputs D3/11 . . . DO18.
A third read operation accesses the low data byte (DB7
. . . DB0) and starts another conversion. The 4 MSB’s
appear on data outputs D11 . . . D8 during all three read
operations above.
Microprocessor Interfacing
The LTC1272 is designed to interface with microproces-
sors as a memory mapped device. The CS and RD control
inputs are common to all peripheral memory interfacing.
The HBEN input serves as a data byte select for 8-bit
processors and is normally connected to the micropro-
cessor address bus.
MC68000 Microprocessor
Figure 18 shows a typical interface for the MC68000. The
LTC1272 is operating in the Slow Memory Mode. Assum-
ing the LTC1272 is located at address C000, then the
following single 16-bit Move instruction both starts a
conversion and reads the conversion result:
Move.W $C000,D0
15
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