PR0=6206        / Execute SBC firmware function
RMDRW=0001      / Read/Write RAM Disk device

/ DTAPE is followed by:
/       Buffer address (DIRBUF)
/       Word Count (negated) (-400)
/       Block Number (2)

/ The "block numbers" here are for 128 word blocks, like those
/ Edu25 Basic was written to use on DECtape.

        FIELD 1
*13200
DTAPE,	0		/ Enter with ac=1 for read
        SNA CLA
        TAD C4000       / Set up for write
        TAD C0010       / Buffers are in Field 1, unit 0
        DCA RMDCNT      / Save for now
	TAD CIFCDF	/ Save calling field for return
	RDF
	DCA DXIT

DGR,	JMS DGET        / Get transfer address
	DCA DCORE	/ ...and store it
	JMS DGET        / Get -number of words
        CIA             / Make it positive
        CLL RAR         / Scale it
        TAD RMDCNT      / Set up transfer size
        DCA RMDCNT
	JMS DGET	/ Get the block number
	DCA RMDPAG	/ ...and store it

        / Do the I/O operation
        PR0
        RMDRW           / Read/write RAM Disk Device
RMDCNT, 0               / R/W bit, page count, buffer field, unit
DCORE,  0               / Address of buffer
RMDPAG, 0               / Starting block number
        SZL             / Error?
        JMP DTERR       / Yes, bail
        JMP DXIT        / No, just return
CIFCDF, CIF CDF
C4000,  4000            / Write needs high bit set
C0010,  0010            / Buffers in field 1, unit == 0

DTERR,	HLT		/ Just crash, for now
	JMP .-1

DXIT=3245
/DXIT,	HLT		/ Return to proper field
/	JMP I DTAPE

DGET=3247
/DGET,	0		/ Pick up next argument
/	TAD I DTAPE
/	ISZ DTAPE
/	JMP I DGET

$