Specifications

8-20
User Patterns and Disk Operation
Disk Operation
Pattern Index
Matches the pattern number minus 4. The pattern in pattern store 9 is stored in file
PATTO5 and has an index of 1 in the pattern number field. Provides a further confidence
check that the file is really the pattern file.
Pattern Label String Length
The label given to the pattern store by the user. The label may contain any eight bit code.
The characters represented by given codes are specified by the display. It is recommended
that only ASCII character codes are used.
Pattern Length
For a straight pattern, this field holds the length of the pattern in bits. The minimum
allowable length is 1. For an alternate pattern, this field holds the length of a pattern, and
not the cumulative length of both patterns. Note: both patterns must have the same length.
See Table 4-1 (on page 4-4) for allowable pattern lengths.
Trigger Bit
The position of the trigger bit within the pattern. The position must be greater than, or
equal to 0, and less than the pattern length.
Type of Pattern
This integer encodes the type of pattern held in the file. At present two types of pattern are
defined:
• Type 0 - straight pattern
• Type 1 - alternate pattern
Pattern Contents
There are two cases to consider, storage of straight patterns and alternate patterns. For
straight patterns, the most significant bit of the first byte contains the first bit of the
pattern. When the pattern length is not an exact multiple of 8, the lesser significant bits of
the last byte are set to zero. The size in bytes of the pattern contents field is the value:
(pattern length ÷8) rounded up to the nearest integer
For alternate patterns, the two patterns are each stored in a format identical to that used for
a straight pattern. The second pattern begins at the byte position after the last byte of the
first pattern.