AT3550 User Guide V1.00
February 11, 2005
page 12 of 16
4.3 POWER
4.3.1 POWER DOWN
Whenever possible, do not power down the computer during a write command
sequence to any mass storage device. This includes during the normal operation
of the drive, and with the use of disk cache programs such as Microsft
®
SmartDrive. If a write routine must interrupted, use the push button reset or a soft
reset. Powering down the AT3550 while it is being written may cause an
incomplete write sequence, and leave as many as 32 sectors with an Address
Mark Found Error or Uncorrectable Errors. DOS will report these with a message
“Error Reading Drive C:”.
4.3.2 POWER SUPPLY
The AT3550 voltage requirement is specified at +5 volts, +/- 5% on the drive itself.
Operation outside of these limits is not guaranteed. Note that the drive will
“operate” down to 4 volts, but reliability issues such as Uncorrectable Errors or
invalid data reads may occur. An on board voltage monitor will inhibit writes when
the supply voltage falls below 4.70 volts, thus preserving data integrity on the
drive.
4.3.3 POWER ROUTING
To avoid “glitches” or noise on the Vcc and ground lines, power in the system
should be routed so that all peripherals are sourced directly from the power supply
as opposed to routing a single continuous supply line to each device in the system
as in daisy chaining. Routing power in the star configuration, as is done on most
desktop PCs, will minimize the effect of one device’s current draw on another
device. This is key to maintaining data integrity on the AT3550. See diagrams
below.
Power Supply
Power Supply
Floppy
Hard Disk
Main Board
Floppy
Hard Disk
Main Board
Star Topology
Daisy Chain - Do Not Use
