3-10-3 Records
The RECORD directive is for defining a bit pattern within a word or byte. It has the form
Record name RECORD Field specification, . . . , Field specification
where each field specification is of the form
Field name: Length = Preassignment
with the preassignment being optional. For example,
PATTERN RECORD OPCODE:5,MODE:3,OPR1:4=8,OPR2:4
would break a word into four fields and give them the names OPCODE, MODE, OPR1, and OPR2. The lengths of the fields in bits would be 5, 3, 4, and 4, respectively.
The statement
INSTRUCTION PATTERN (,,,5)
would actually reserve the word, associate it with the variable INSTRUCTION, and preassign OPR1 to 8 and OPR2 to 5 as shown in Fig. 3-61.
Figure 3-61 Typical use of RECORD to subdivide a word.
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