The TLL adapter basically emulates COM port on USB right? If so, can I just connect the seagate drive interface directly to a COM port on my PC? I'm planning to use a PC with Windows XP or 7.

that would suck

COM port uses +-12V signaling, which would kill the pcb instantly...
you need to match IO voltage to that of the pcb.

pepe

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Adatmentés - Data recovery

Do you know the IO voltage of the Seagate ST310014ACE drive by any chance? I'm new to unlocking by TLL adaptor.

Measure it. I'm guessing it will be 3.3V.

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A backup a day keeps DR away.

On the EEPROM or somewhere else on the PCB? I couldn't find any info of where to measure it.

Just measure the Tx/Rx pins. One or both will be sitting at the Vio supply rail.

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A backup a day keeps DR away.

Pins 8,6,2 are sitting at 5v. Pin 4 is the only 3.3v and pin 3 (the pin above it) sits at 5v. Rest show 0 volts. Will the pin 4 be the i/o voltage?

I wasn't expecting to see 5V.

The ROM's Vcc pin would be the Vio voltage. I would use a 3.3V TTL adaptor.

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A backup a day keeps DR away.

Just making sure I pick the right one. I found some TLL adapters. One is a MAX232 without pins for 3.3v and 5v that plugs directly to COM (description says it supports voltages from 3.3 to 5v) and an PL2303 based one with seperate pins for 3.3v and 5v (USB interface), which seller listed as UART USB TLL RS232 adaptor. Which one is the correct one?

I would purchase a USB-TTL adaptor, but either should work. You can also find adaptors with multiple selectable I/O voltages (1.8V, 2.5V, 3.3V).

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A backup a day keeps DR away.