Some Seagate drives based on Barracuda architecture can function both in COM and ATA terminal modes.
Their list includes U5, Barracuda I – IV. At power-on such drives immediately switch to work via COM port.

While running in COM terminal mode the drive has to be connected to PC COM port via the PC-KALOK adapter or to a USB port via the PC-USB-TERMINAL adapter (the PC-USB-TERMINAL driver is included into the software package). USB connection allows better stability and much faster data transfer rates than PC-KALOK (up to 921000 Kbaud in 7200.7 and U series 7). The drives begin operating in COM terminal as soon as power supply it turned on. You can enter the actual command mode by pressing [Ctrl]+[Z] in terminal. The drive will respond with “T>” prompt, then you can enter terminal commands.

While operating in the ATA terminal mode, a drive has to be connected to PC with a standard ATA cable used
for all data transfer purposes. HDD enters the ATA terminal mode after receipt of a respective factory (techno) ATA
command. Therefore, to enter the ATA terminal mode, the drive has to report on readiness via its ATA interface.
Basically, that mode should have provided for a considerable increase in data transfer rate. Still, as we have noted
above, some peculiarities in drive microprogram operation cause the transfer rate to remain at the transfer rate typical of COM terminal running at 57600. Besides, drive designers discontinued using the ATA terminal optimizing instead the micropogram and improving the sustained rate of transfer via COM port.

For Segate HDD repair and data recovery, there’re currently two professional hdd repair tools out there in the market, HD Doctor for Seagate and PC3k UDMA, they both support drive diagnosis, firmware repair, password removal, etc.

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