using the bootstrap loader

WRITING A CUSTOM FIRST-STAGE DRIVER
5-28
/************************************************************
* This example reads the general purpose register of the *
* unit definition record within the interconnect space *
* found on the board in slot number three. Note that *
* this code does no checking of status after each call to *
* BS$GET$INTERCONNECT. The programmer must ensure the *
* value returned is correct. *
************************************************************/
SAMPLE_BS$GET$INTERCONNECT: DO;
DECLARE slot$number BYTE;
DECLARE record$offset WORD;
DECLARE unit$def$rec BYTE;
DECLARE rec$length$reg$off BYTE;
DECLARE gen$status$reg$off BYTE;
DECLARE record$found BYTE;
DECLARE eot$rec BYTE;
DECLARE status WORD;
DECLARE value BYTE;
DECLARE slot LITERALLY '3R';
DECLARE udr LITERALLY 'OFER';
DECLARE gsro LITERALLY 'OAH' ;
DECLARE eotrec LITERALLY , OFFH' ;
DECLARE rlro LITERALLY 'OIR';
DECLARE ro LITERALLY '020H';
CODE: DO;
slot$number
unit$def$rec
gen$status$reg$off =
eot$rec
rec$length$reg$off =
slot;
udr;
gsro;
eotrec;
rlro;
/***********************************************************
* Set up to read the first nonheader record within the *
* interconnect space. This is done by establishing *
* record$offset past the interconnect space header *
* record, which in this case is 32 bytes long. *
***********************************************************/
record$offset = ro;
Bootstrap Loader
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