23
LTC1417
TYPICAL APPLICATIONS
U
Figure 21 shows the connections necessary for interfacing
the LTC1417 and LTC1391 8-channel signal acquisition
system to an SPI port. With the sample software routine
shown in Listing A, the SPI uses MOSI to send serial data
to the LTC1391 8-channel multiplexer, selecting one of
eight MUX channels.
While data is sent to the LTC1391, SPI uses MISO to
retrieve conversion data from the LTC1417. After the data
transfer is complete, the conversion start signal is sent to
the LTC1417. The end of conversion is signaled by a logic
high on the BUSY output. When this occurs, data is
exchanged between the LTC1417/LTC1391 and the
controller.
The timing diagram in Figure 22 shows the relation be-
tween MUX channel selection data and the conversion
data that are simultaneously exchanged. There is a two
conversion delay between the MUX data selects a given
channel and when that channel’s data is retrieved.
Figure 21. 0V to 4.096V, 8-Channel Data Acquisition System Configured
for Control and Data Retrieval by a 68HC11 µC. Code is Shown in Listing A
1417 F21
1µF
10µF
5V
10µF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LTC1417
5V5V
NC
NC
PORT C, BIT 7
PORT C, BIT 0
SS
MISO
MC68HC11
CLK
MOSI
A
IN
+
A
IN
–
V
REF
REFCOMP
AGND
EXTCLKIN
SCLK
CLKOUT
V
DD
V
SS
BUSY
CONVST
RD
SHDN
DGND
D
OUT
LTC1391
S0
S1
S2
S3
S4
S5
S6
S7
16
15
14
13
12
11
10
9
V
+
D
V
–
D
OUT
D
IN
CS
CLK
DGND
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
1
2
3
4
5
6
7
8
0.1µF