HP 7925D Service Manual page 81

7925
Troubleshooting
Table 4-2. Disc Service Unit CDSU) FunctionsCContinued)
CONTROL/
INDICATOR
STOP pushbutton
DELAY control
3-digit display
FUNCTION switch
START (STROBE)
pushbutton
STOP pushbutton
3-digit display
FUNCTION switch
START (STROBE)
pushbutton
Upper 4 toggle
switches
(TO through T3)
TO thru T3 LED
indicators
FUNCTION
Function No.3 - Random Seek (Continued)
Stops operation of Random Seek function.
Selects time interval between seeks.
Indicates time interval between seeks. Readout is in milliseconds.
Function No.4, 5, or 6 - Circumferential Alignment
Selects automatic setting to prescribed cylinder depending on the position.
Position 4 - cylinder 0
Position 5 - cylinder 410
Position 6 - cylinder 820
Starts operation. Heads go to the cylinder listed above.
Stops operation.
Indicates time interval to seek to the cylinder. Readout is in milliseconds.
Function No.8 - Manual Mode
Selects Manual mode of operation (position 8).
When pressed, activates STROBE signal applied to the tag bus decoder in I/O Sec-
tor PCA-A2. This executes the command selected by tag bus switches 64 through
512 on the upper bank of 10 toggle switches. The STROBE signal is active as long
as the START (STROBE) pushbutton is held down.
Selects input command to be supplied on tag bus to drive. The toggle switch set-
tings and the associated input commands are listed on the upper right-hand corner
of the DSU front panel. The DSU does not issue a Write command.
Indicates the state of the tag bus bits (input command) selected by the upper 4
toggle switches (64 through 512).
Selects state 'of control bus bits CO through C15 for the following tag bus com-
mands. Bits are strobed into the drive when the START (STROBE) pushbutton is
pressed.
Lower bank of 16
toggle switches
(1 through 512
and 1 through 32)
Command
Address Record
(ADR) - 1001
CO thru C5
C8, C9, C10,
and C11
Control Bits
Selects sector address to be stored in drive
Sector Address register.
Selects head identity to be stored in drive
Head register.
Note: On functions 1 through 3, head 0 and sector 0 are selected before the initial seek to 0 (zero).
4-7