[Coco] hpn/hpa drive descriptor parameters?

[Roger Taylor]

I'm trying to figure out a little more about the hpn and hpa 
parameters used by Dmode, and how to access the bytes from my driver.

My initial assumption was that I could reference these bytes by using 
a negative offset from the option table address ,y
However, my driver isn't acting on the changes to hpn when I use 
Dmode /dd hpn=80   and hpn=0 to toggle a feature.

Am I crazy to assume the following based on 0,y being the address of PD.DTP ?

-4,y  hpn ?
-3,y  hpa ?
-1,y  # of bytes of options ??
PD.DTP  0,y
PD.DRV 1,y


	mod	DescEnd,DescName,Type,Revs,DscMgr,DscDrv
	fcb	DIR.+SHARE.+PREAD.+PWRIT.+UPDAT.+EXEC.+PEXEC.

	fcb	$00		port bank
	fdb	$ff6c		port address
	fcb	OptEnd-*-1	number of bytes in option section below

* OPTION TABLE
	fcb	DT.RBF     	device type = RBF				0 offsets
	fcb	Drive      	disk # in current partition			1
	fcb	StpRat     	step rate code					2
	fcb	DrvTyp    							3
	fcb	Density   							4
	fdb	Cyls       	number of cylinders				5
	fcb	Sides     							7
	fcb	Verify     	verify						8
-- 
~ Roger Taylor
http://liveshots.blogs.foxnews.com/2010/05/12/on-the-job-hunt-ups/?test=latestnews