Datasheet
17
LTC1273
LTC1275/LTC1276
127356fa
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
OLD DATA
DB7-DB0
NEW DATA
DB7-DB0
TRACK
HOLD
DATA
BUSY
RD
CS
RD
LTC1273/75/76 • F14
t
8
t
1
t
2
t
3
t
CONV
t
11
t
9
t
8
t
9
t
5
t
1
t
4
t
5
t
10
t
10
t
6
t
7
t
3
t
7
t
12
t
12
HBEN
NEW DATA
DB11-DB8
Figure 14. Slow Memory Mode, Two Byte Read Timing Diagram
Table 3. Slow Memory Mode, Two Byte Read Data Bus Status
Data Outputs D7 D6 D5 D4 D3/11 D2/10 D1/9 D0/8
First Read DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Second Read Low Low Low Low DB11 DB10 DB9 DB8
that the 4MSBs appear on data output D11...D8 during
both READ operations.
ROM Mode, Parallel Read (HBEN = LOW)
The ROM Mode avoids placing a microprocessor into a
WAIT state. A conversion is started with a READ opera-
tion, and the 12 bits of data from the previous conversion
are available on data outputs D11...D0/8 (see Figure 15
and Table 4). This data may be disregarded if not re-
quired. A second READ operation reads the new data
(DB11...DB0) and starts another conversion. A delay at
least as long as the ADC’s conversion time plus the 600ns
minimum delay between conversions must be allowed
between READ operations.
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 16 timing diagram and Table 5 data bus status).
Two more READ operations are required to access the new
conversion result. A delay equal at the ADCs’ conversion
time must be allowed between conversion start and the
third data READ operation. The second READ operation
with HBEN high disables conversion start and places the
high byte (4MSBs) on data outputs D3/11...D0/8. A third
read operation accesses the low data byte (DB7...DB0)
and starts another conversion. The 4MSBs appear on data
outputs D11...D8 during all three read operations.
MICROPROCESSOR INTERFACING
The LTC1273/LTC1275/LTC1276 allow easy interfac-
ing to digital signal processors as well as modern high
speed, 8-bit or 16-bit microprocessors. Here are sev-
eral examples.