RK06/RK07 Disk Drive User's Manual - Trailing-Edge

Multiple Drive Select Line
When asserted, this line indicates to the controller that more than one drive has simultaneously responded
to a given selection code. To accomplish this, a selected drive monitors the Index/Sector pulse
line for the presence of extraneous pulses. If pulses other than those originating from the desired drive
are detected, the Multiple Drive Select line is asserted. However, since Index/Sector pulses cannot be
generated if the heads of the desired drive are not loaded, the drive uses Control Clock pulses, inserted
on the Index/Sector pulse line, to monitor and detect multiple selections.
Finally, the Multiple Drive Select signal is asserted within 300 ns of pulse detection from another drive
and negated within 120 ns after the receipt of another message strobe.
Initialize Line
When asserted, this signal deselects all drives, resets all error conditons, and clears the Drive Status­
Change flip-flop.
Controller Power on Line
When asserted, this line indicates that power has been applied to the controller, and a physical connection
(via cable) has been established between the controller and the available drives. When the line
is negated, all drives are deselected, and the Strobe and Control Clock logic is disabled in the drive to
prevent any erroneous drive selection.
2.5.2 Subsystem Commands
The 13 subsystem commands (Figure 2-4) can be divided into two basic groups. One group (nondata
handling) is concerned with the various operational requirements of the drives, while the second group
(data or header handling) is concerned with the transfer of data and header information to or from a
selected device.
2.5.3 Data Formatting
When the tracks of a disk are formatted via separate Write Header commands, the following information
is recorded to identify each sector in relation to its radial and rotational position on a disk (Figure
2-3).
1. The Header Preamble field contains 16 words, consisting of 255 Zero bits and a single One
bit (SYNC) that defines the start of valid information.
2. The Header field consists of two words:
a. Word 1 contains the cylinder address which defines the radial location of the sector in
relation to the 411 (for the RK06) or 815 (for the RK07) addressable cylinders on the
disk.
b. Word 2 contains the sector address-which defines the sector in relation to the number
(20 or 22) of sectors per track-and the track address, which defines one of the three
R/W heads (and therefore the appropriate R/W surface in relation to the disks) a
Format (FMT) bit that is a zero to reflect 16-bit data, or a one to reflect 18-bit data
words. Finally, the Good Sector flag (GS FLAG) bits are set to indicate that the sector
is valid for the reading or writing of data.
3. The Header Check field consists of one word that is an exclusive-OR sum of header words 1
and 2. The check word is generated by software and extracted during read operations to
verify the integrity of both the Header field and the check word.
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