using the bootstrap loader

WRITING A CUSTOM THIRD-STAGE DRIVER
6.3 DEVICE INITIALIZATION PROCEDURE
6-4
The device initialization procedure must present the following PL/M-86 interface to the
third stage:
device$init: PROCEDURE (unit) WORD PUBLIC;
DECLARE unit WORD;
END device$init;
where:
device$init
unit
(code as described below)
The name of the device initialization procedure. You can choose any
name you wish for this procedure, as long as the names of other thirdstage
procedures do not conflict.
The device unit number as defined during Bootstrap Loader
configuration.
The WORD value returned by the procedure must be the device granularity, in bytes, if the
device is ready, or zero if the device is not ready.
The third-stage device driver initialization procedure, (like the first-stage device
initialization procedure) must do the following operations:
1. Test to see if the device is present. If the device is not present, return the value zero.
2. Initialize the device for reading. This is a device-dependent operation. For guidance
in initializing the device, refer to the hardware reference manual for the device.
3. Test to see if device initialization was successful. If it was not, return the value zero.
4. Read the device volume label to obtain the device granularity. (For information on
the location and organization of the volume label, see the iRM)(® Disk Verification
Utility Manual.)
5. If the attempt to obtain the device granularity was successful, return the device
granularity. Otherwise, return the value zero.
NOTE
Besides the above five steps, the procedure must follow MUL TIBUS II
transport protocol and belong to the BSL-Drivers COMPACT sub-system if the
driver functions in a MULTIBUS II environment. Refer to Section 5.5 for
more information on these two requirements.
Bootstrap Loader
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