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HD9626DSK Instruction Manual
Alternately, the user can connect an external power source for the Opto-isolator circuitry. The Vext
voltage must be greater than the voltage supplied to GPI by at least 3v. Figure 2-4 and Figure 2-6
show how to wire the GPIs and GPOs from an external power supply.
The tally outputs are active low and require an external pull up (10k Ohm) resistor to the Vext pin.
When active, the output will go low and is able to sink up to 10mA. When inactive, the signal will go
high (to the voltage applied to the Vext pin). Do not attempt to source more than 100µA from the
output.
Table 2-8 shows the maximum limits that the user must adhere to so that no circuitry is damaged.
Description
Maximum GP+3.3V current
load
Minimum input voltage for a high
Maximum input voltage for a low
Maximum GPO sink current
All GPI inputs are level triggered. Lowering the GPI input to a potential below Vext will select the
allocated preset definition. The 8 GPIs (A through H) can be used to activate various functions such as
logo control, voiceover, transition, etc. If multiple inputs are active both commands are ignored until a
single input is recognized.
The GPI to logo allocation is programmable from the front panel of the HD9626DSK. (See section
3.9.5).
Page 2-8
Name
I
max
GP+3.3V
V
high min
gpi
V
low max
gpi
I
max
gpo
Table 2-8: GPIO Maximum Ratings
Revision 1.4
Value
100 mA
3 V
0.8 V
25 mA
INSTALLATION
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