HIGHLY LIQUID UMR2 User Manual - Page 7

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3.2.5 Matrix Polarity Jumper

CAUTION: Failure to set or incorrect setting of the Matrix Polarity Jumper can permanently
damage the UMR2 and host keyboard.
The Matrix Polarity Jumper serves two functions:
Configures the built-in resistors connected to all UMR2 Matrix Select and Matrix Data terminals
•
as either pull-up or pull-down resistors.
Controls the logic state (low or high) of signals generated by the UMR2 at the Matrix Data I/O
•
Terminals.
Use a piece of wire to connect only one side of the jumper as shown in the diagrams below.
Details for specific keyboards can be found at the
Active High Select / Common Anode Matrix
Use this jumper setting if the host
keyboard generates high-state logic
pulses at the select lines when
reading the switch matrix.
UMR2 built-in resistors act as pull-
downs.
Active Low Select / Common Cathode Matrix
Use this jumper setting if the host
keyboard generates low-state logic
pulses at the select lines when
reading the switch matrix.
UMR2 built-in resistors act as pull-
ups.
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