A cou ple of ex am ples might help to il lus trate. Sup pose we're boot ing from a floppy or hard disk and
we have in stalled two 512K X 8 SRAMs. In or der to cre ate the de sired 1 Meg RAM DISK we would
need the line :
de vice = ussd.sys /mod:p /seg:e400 /psz:16 /inc:1 /pad:1ec /spg:80 /dsz:1024
which would in di cate that we wish to cre ate a disk of 1M (1024K) start ing at the be gin ning of the ar
-
ray.
For an other ex am ple as sume that we want a 512K ROM DISK and a 512K RAM DISK. We would
cre ate our boota ble floppy with the CON FIG.SYS line :
de vice = ussd.sys /mod:p /pad:1ec /seg:e400 /psz:16 /inc:1 /spg:a0 /dsz:512
This would cre ate the 512K RAM DISK which will be pre ceded by the 512K of ROM DISK. We
would cre ate our ROM DISK as pre vi ously de scribed and place the EPROM into U27. We would in stall
our 512K SRAM into U23.
A fi nal ex am ple would be to use the non- bootable RAM DISK in U27 as a sec on dary sili con disk to
a DISK-ON-CHIP. In this case we are boot ing from the DISK- ON- CHIP and will in clude the fol low -
ing CON FIG.SYS com mand line :
de vice = ussd.sys /mod:p /seg:e000 /psz:16 /inc:1 /pad:1ec /spg:80 /dsz:512
this will cre ate a 512K RAM DISK in the sili con disk socket U27.
NOTE : USSD, as is the con ven tion with DOS instal la ble disk de vices, cre ates a drive with the
NEXT AVAIL ABLE drive let ter. Drives A: and B: are al ways re served for the physi cal floppy drive or
the BIOS sup ported boota ble Sili con Disk. In a sys tem with out a hard disk, the next avail able drive let
-
ter would be C:. In a sys tem with one or more hard drive par ti tions, the sili con disk cre ated with USSD
will be the first avail able let ter fol low ing any other drive let ters al ready in use. Also note that it is never
nec es sary to for mat a disk cre ated with USSD. The disks are self for mat ting us ing the size and ad dress
in for ma tion pro vided on the CON FIG.SYS in vo ca tion line. Dur ing ini tiali za tion, USSD ex am ines the
sili con disk to de ter mine if a disk al ready ex ists which matches the pa rame ters speci fied. If so, no ac tion
is taken and the disk is used as is. If there is not a disk of the type and size speci fied, it is cre ated.
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OPERATIONS MANUAL LBC-Plus
991206
WinSystems - "The Embedded Systems Authority"
