AN1235 Rev 0.00
Page 4 of 7
Feb 2, 2006
ISL59481EVAL1
Internal and External Channel Select Logic
J-S0, J-S1 and J-S2 are two-position jumpers that control the
method of channel selection. In the AUTO position, the internal
channel scan is enabled. The MANUAL position connects the
on-board SPDT switches (S0, S1, and S2) for manual
selection. A parallel-connected EXTERNAL CONTROL ribbon
cable header is provided for external channel select control.
A wide range of auto-scan options can be selected by
connecting only 1 or 2 of the 3 jumpers to the internal logic,
with the remainder connected to the switch. For example,
connecting jumper J-S0 to the AUTO position and connecting
jumpers J-S1 and J-S2 to the MANUAL position with the
switches S1 and S2 to the logic 0 state limits the channel scan
to only 2 of the 8 channels (IN0 and IN1). Moving a second
jumper from the MANUAL position to the AUTO position,
increases the number of channels scanned from 2 to 4. The
complete list of channel scan jumper options are shown in
Table 2.
FIGURE 3. CHANNEL SCAN OSCILLATOR
U4C
5
6
R1
J1
S4
C1
AUTO-
STEP
SINGLE-
STEP
TO BINARY
COUNTER CLK
MOMENTARY
CONTACT SWITCH
2.2M
1µF
TABLE 2. CHANNEL SCAN SELECT LOGIC TABLE
CHANNELS
SCANNED
JUMPER POSITION
SWITCH POSITION
CHANNELS SELECTED
J-S2
J-S1
J-S0
S2
S1
S0
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
8
Auto
Auto
Auto
-
-
-
X
X
X
X
X
X
X
X
4
Manual
Auto
Auto
0
-
-
X
X
X
X
Manual
Auto
Auto
1
-
-
X
X
X
X
Auto
Manual
Auto
-
0
-
X
X
X
X
Auto
Manual
Auto
-
1
-
X
X
X
X
Auto
Auto
Manual
-
-
0
X
X
X
X
Auto
Auto
Manual
-
-
1
X
X
X
X
2
Manual Manual
Auto
0
0
-
X
X
Manual Manual
Auto
0
1
-
X
X
Manual Manual
Auto
1
0
-
X
X
Manual Manual
Auto
1
1
-
X
X
Auto
Manual Manual
-
0
0
X
X
Auto
Manual Manual
-
0
1
X
X
Auto
Manual Manual
-
1
0
X
X
Auto
Manual Manual
-
1
1
X
X
Manual
Auto
Manual
0
-
0
X
X
Manual
Auto
Manual
0
-
1
X
X
Manual
Auto
Manual
1
-
0
X
X
Manual
Auto
Manual
1
-
1
X
X
