CPC7508
1.10 Truth Table
TEST
BRIDGE
Switches
Break
Switches
TEST_OUT
Switches
TEST_IN
Switches
IN
IN
IN
T
SD
State
LATCH
A
B
C
Talk
0
0
0
0
1
1
1
1
X
X
0
0
1
1
0
0
1
1
X
X
0
1
0
1
0
1
0
1
X
X
On
Off
Off
On
On
Off
Off
Off
Off
Off
On
Off
On
On
Off
Off
Off
Off
Off
Off
Off
Off
Off
On
Off
On
Off
On
Off
On
Off
On
TEST_IN
TEST_OUT
TEST_IN Monitor
TEST_OUT Monitor
TEST_IN & OUT
All-Off
0
1
Z
TEST_IN Bridge
Latched
1
Unchanged
All-Off
X
0
Off
Off
Off
Off
1 Z = High Impedance. Because TSD has a high impedance output for a logic high it needs to be pulled up to the logic supply through an external resistor.
Break Switches: SW1 and SW2
TEST_OUT Switches: SW3 and SW4
TEST_IN Switches: SW5 and SW6
TEST BRIDGE Switches: SW7 and SW8
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