RANA Systems Elite Controller, User Manual

Page: 171 / 328

ELITE SERIES USER MANUAL THEORY OF OPERATION
7 . 2 . 2 . B o o t i n g
The Rana boot code automatically detects the
format, whether 13 or 16 sector, and loads the
initial boot sector (track 0, sector 0).
On 13 sector booting, control is immediately
transferred to the second stage boot code
(loaded at $300—$3FF) via a jump to $301.
On 16 sector booting, the boot sector is loaded
at $800—$8FF. Following the load, byte $800 is
checked to find which other sectors are to be
loaded prior to transferring control to the
second stage. Any additional sectors will be
loaded in successive memory pages ($900, $AOO,
etc).
The standard DOS 3.3 second stage boot does not
require any additional sectors to be loaded
under the exclusive control of the boot PROM.
Once all the required sectors have been loaded,
the PROM transfers control to the second stage
boot code via a jump to $801.
Both the DOS 3.2.1 and DOS 3.3 second stage boot
routines re-enter the boot PROM in order to use
the sector reading code it contains.
DOS 3.2.1 re-enters the PROM at $Cn5D using a
6502 JSR which requires the PROM to perform an
RTS when completed.
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