just asking for some reassurance really, probably a novice question. Thank you in advance for any advice.

I am building this project:


to control a SID audio chip from a Commodore 64 via a Teensy microcontroller. I have the project working and can control the chip via usb midi. Next I would like to add some flashing lights in the form of some LEDS to visually demonstrate it functioning.

I have the data sheet for the IC: http://archive.6502.org/datasheets/mos_6582_sid.pdf

I intend to add power LEDs for the two power supplies (5v and 9v)

my thinking is that I can also add eight LEDs (and resistors) for pins d0-7 on the chip which will light as data is being sent to these pinsr. In theory I would connect the anodes to the pins, and cathodes via a resistor to ground.

My concern is that the LEDs may themselves interfere with the data being transferred. Some my questions are really; Is there any way to be sure of this other than experimenting with resistor values? Am I missing something and am actually likely to destroy the IC? Would pins A0-A4 be any different?

the doc has this to say about pins D0-D7.

"D0-D7 (Pins 15-22) — These bidirectional lines are used to transfer data between SID and the microprocessor. They are TTL compatible in the output mode and capable of driving 2 TTL loads in the output mode. The data buffers are usually in the high-impedance off state. During a Write operation, the data buffers remain in the off (input) state and the microprocessor supplies data to SID over these lines. During a Read operation, the data buffers turn on and SID supplies data to the microprocessor over these lines. The pins are normally connected to the corresponding data lines of the microprocessor."


Just add a buffer chip, like CD74ACT244, to drive the LEDs.


Minimal load on the source device, plenty of output current to drive LEDs.

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