Table of Contents
Advertisement
PROGRAMMING CONVENTIONS
In writing programs for the DATANET-30, there are a few conventions which should be con-
sidered.
The suggestions made here are not hard and fast rules, but must be considered for
maximum programming efficiency:
1.
Do not use locations 0 and 1 in memory; these locations are used by program interrupt.
When the Q-counter counts down to zero, P+l is stored in location 0 and control is
transferred to the location specified by location 1.
2. · Do not use cells 3, 4, and 5. These locations are used by the controller selector unit
for storage of command words.
3.
If
possible, all subroutine linkages and constants should be located in the common
data bank (cells 8 - 511 in memory).
4.
Channel tables must be located in the first 8.192 wqrds of memory.
5.
utility routines should be stored at the top of the memory, so that they will not be
destroyed when reading in later programs.
6.
The following checks should be made:
a.
Before issuing any SEL instruction, check the ready status of the controller with
the CSR instructlOil.
b.
Before issuing any CSR instruction, check for the completion of the previous
SEL sequence with an NIS
7
instruction.
c.
Before changing memory locations 3, 4,
~d
5, check for completion of the previous
SEL sequence with an NIS 7 instruction.
7.
When closing a file on magnetic tape always write an end of file on the tape.
8.
When branching to
a
subroutine, the symbolic name of the subroutine link will be followed
by 1:
REP RT
BRS
IND 0
IND
REP RT
REPRTl
Go to report subroutine
Subroutine linkage
REPRT 1 is the actual starting
address of the subroutine.
9.
The last character to be transmitted at the end of transmitting a message must be
an all marks character (all l's).
10.
At the end of each program bank, careful consideration should be given to the instructions
in the last 2 positions and to those instructions that fell into the succeeding program
bank.
[ID!A\1J!A\~~1J~ ~@------------
V-6
Advertisement
Table of Contents
