Table of Contents
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1 PROGRAM INTERFACE
This chapter contains information required to write disk
I/o programs for the Cartridge Disk System.
It includes
descriptions of the device orders, summaries of the key
events that may occur during I/o operations, and tables
that define the status response for the I/o instructions. The
section entitled "Additional Programming Considerations"
contains information relating to the protection of recorded
information, to command chaining and data chaining, and
to the I/o interrupt environment. The chapter ends with
a series of logic diagrams, one for each device order.
DEVICE ORDERS
When the controller successfu Ily completes the execution of
an SIO instruction or a command chain, it makes an order-
out service call to the lOP to obtain the order for the next
operation (see "Service Cycles" in Chapter 2). Table 5
lists the decoding af the orders. Any other code in the
order byte is treated as an invalid order.
Tab Ie 5. Orders
Binary Representation
Bit Positions
Hexadecimal
Order
o
1 2 345 6 7
Code
Write
o
0 0
0
0
0
0 1
X'Ol'
Read
o
0 0 0 0 0 1 0
X'02'
Seek
00000011
X'03'
Sense
o
0 0 0 0 100
X'04'
Check-write
o
0 0 001 0 1
X'05'
Read
000 100
1
0
X'12'
Test
00010011
X'13'
WRITE (X'01')
The Write order writes on the disk the number of data bytes
specified by the byte count field in the lOCO.
The data
to be recorded must be in the I/O Table in memory, starting
at the address indicated in the lOCO. The data bytes will
be written beginning at the track and sector addresses cur-
rently in the controller address register.
These addresses
are determined by the previous Seek order or by the last
sector accessed, incremented by
1.
Data transmission con-
tinues until the controller indicates to the disk drive that
the entire record has been transmitted.
When a record requires more than one sector, the controller
automatically increments the track and sector addresses and
continues writing in the next sector (see "Data Access" in
14
Program Interface
Chapter 2).
If the record does not requ ire the entire last
sector, the controller zero-fills the remainder of that sector.
'Nhenever on operation is attempted to a write-protected
disk, that operation is not performed and the condition is
reported (see "Status Response" later in this chapter).
READ (X'02')
This Read order reads from the disk the number of data bytes
specified by the byte count field in the lOCO.
The data
wi II be stored in the I/O Table in memory, starting at the
address indicated in the lOCO. The data bytes wi" be read
beginning at the track and sector addresses currently in the
controller address register. These addresses are determined
by the previous Seek order or by the last sector accessed,
incremented by
1.
Data transmission continues until the
byte count is reduced to zero.
When the byte count in the lOCO is greater than 360, the
controller wi II automatically increment the track and sector
addresses, and continue reading the next sector (see "Data
Access
II
in Chapter 2) •
For this Read order, any transmission error encountered is
reported at count done (see "Status Response" later in this
chapter) •
SEEK (X'03')
The Seek order sends two bytes to the controller where they
are loaded into the address register. The two bytes must be
in the I/o Table in memory, starting at the addr1ss specified
in the lOCO.
After a Seek order is issued, the controller
directs any subsequent read/write operation to
b~gin
at the
specified track and sector addresses.
I
The format of the two bytes sent to the controller by a Seek
order must be
Byte 2
sector
34
7
where
track
specifies the desired track address and must be
within the range 0 - 407
10
•
sector
specifies the desired sector address and must
be within the range 0 -
15
10
•
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