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Summary
Summary
This is the schematic for the A600 and A1200 LED circuit. _IDE_LED is the active low signal for the HDD LED.
Here is a simulation of the _IDE_LED signal circuit. The normal signal level on the Amiga is L = 0V and H = 5V. Click on the H input signal to change it from H (Hi) to L (Lo). Since _IDE_LED is active low, when this signal is Lo then the HDD LED will turn on.
HDD LED Constantly On
HDD LED Constantly On
The Amiga uses CMOS signal levels, which is essentially means Lo is 0V and Hi is 5V, but its actual Hi range is 3.5V, and anything below 3.5V may be considered Lo.
IDE CF adapters that output 0V and 5V signal levels will work OK. However, some adapters work only at 3.3v, and their signal levels are Lo is 0V and Hi is 3.3V. Such adapters will cause the HDD LED to be on all the time, since 3.3V will be considered Lo for the _IDE_LED signal.
See the following for more details.
Below is a simulation of the _IDE_LED signal circuit and the various scenarios. Use the switch to select between the options.
#1 Normal behaviour - IDE/CF adaptor sends L=0V and Hi=5V for _IDE_LED signal.
#2 Abnormal behaviour - IDE/CF adaptors sends L=0V and Hi=3.3V for _IDE_LED signal.
#3 Fix for 3.3V based IDE/CF adaptors - a an inline resistor. Use the potentiometer to change the resistance to the desired LED contrast between Lo and Hi.
HDD LED Doesn't Come On
HDD LED Doesn't Come On
https://www.tsb.space/knowledge-base/compact-flash-led-not-working/
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