[code:1:07be22c134]
Bit at $FF40 Function
0 drive select 0
1 " 1
2 " 2
3 motor enable: 0=off, 1=on
4 write precomp: 0=off, 1=on
5 density flag: 0=single, 1=double (normal Coco)
6 drive select 3
7 halt flag: 0=disabled, 1=enabled[/code:1:07be22c134]

If this is not ok to post, let me know, I will delete it.
Dave

Disk Basic Summary
————————————————————————
Disk management commands

BACKUP n TO m Copy all files from one disk to another

BACKUP n BACKUP a disk using only a single disk drive

COPY file1 TO file2 Make a duplicate of a file

DIR n List the files that are on the disk

DRIVE n Use drive n as the default

DSKINIn Initialize (format) a disk

KILL file Delete a file from the disk

LOAD file,R Load a program, and optionally start it running

LOADM file,offset Load a machine-code program, shifting by offset

MERGE file,R Load an ASCII program without clearing the old one

RENAME file1 TO file2 Change the name of a file

RUN file,R Load a program, and optionally start it running

SAVE file,A Save a program, optionally in ASCII

SAVEM file,a1,a2,ax Save a machine-code program, from a1 to a2, exec at ax

VERIFY ON Double-check all writes to the disk

VERIFY OFF Don’t double-check

Programming commands

FILES max_f,size Reserve buffers for open files

FREE(n) Returns the number of free granules (2304 bytes each)

UNLOAD n Close all open files on drive n

DSKI$ n,t,s,v1$,v2$ Read track t sector s into v1$ and v2$

DSKO$ n,t,s,v1$,v2$ Write track t sector s from v1$ and v2$

OPEN “I”,f,file Open a file for sequential input (ie: INPUT)

OPEN “O”,f,file Open a file for sequential output (ie: PRINT/WRITE)

OPEN “D”,f,file,len Open a file for direct access; (ie: GET/PUT);

record length len is optional

CLOSE #f Close a file

Sequential file commands

EOF(f) Returns true if file f has been read to the end

INPUT #f, var,… Read variables from a file

LINE INPUT #f,var$ Read an entire line from a file into a string variable

WRITE #f,values Write values to file, with commas, strings in quotes,…

PRINT #f,values Write values to file, just as PRINT would display them

PRINT #f,USING f$;values Formatted printing; many options for f$

Direct-access file commands

FIELD #f, size AS v$,… Give variable names to parts of the file buffer

RSET v$ = value$ Fill in a named part of the file buffer, right-justified

LSET v$ = value$ Fill in …, left justified

PUT #f,r Write the buffer to record r

GET #f,r Read record r into the buffer

CVN(var$) Make a number out of a binary string

MKN$(num) Make a binary string out of a number

LOC(f) Return the current record number in the buffer

LOF(f) Return the highest record number in the file

In all cases, f is a file number, n and m are drive numbers, file is a

filename, and dollar signs signify variables that must be string-variables.

Note that filenames must be either string variables or string constants in

quotes. Upper-case words are keywords, lower-case words are supplied by the

user.

Special file numbers are -2=printer -1=cassette and 0=screen

————————————————————————

Syntax for a filename, in BNF. (Things in square brackets are optional, the

vertical bar separates alternatives, angle brackets surround nonterminals,

and uppercase words denote single-letter constants.)

::= [(DOT|SLASH) ] [COLON ]

The name can be up to eight characters long, and cannot include a dot,

slash, colon, or zero. The extension can be up to three characters long,

and also cannot include those four characters. The drive number is a single

digit, from zero up to the highest drive on your system.

————————————————————————

There is one documented subroutine in the Disk BASIC ROM that you can use

to access the disk. Its address is stored at $C004 and $C005, so you jump

to it using indirection: JSR [$C004] .

Before calling that, you should load the X register with the address of a

data structure that describes what you want to do. The examples in the

manual always load this address from locations $C006 and $C007. I have not

tried using this, so I don’t know it will work if you put your structure

anyplace else. This data structure is seven bytes long:

1 byte op code (0 – 3)

1 byte drive number (0 – 3)

1 byte track number (0 – 34)

1 byte sector number (1 – 18)

2 bytes address of 128-byte data buffer

1 byte error code

Op codes are either 0 (restore to track 0), 1 (no op), 2 (read sector), or

3 (write sector).

Bits in the error code are defined as follows (since the labels match those

in the 1771 data sheet, I assume it is just the 1771 status code being

returned, and have taken the much more complete descriptions from that data

sheet). Note that some of the bits have different meanings based on which

command caused them to be set.

7 Not Ready

This bit, when set, indicates that the disk drive is

not ready to perform a read or write operation. When

reset it indicates that the drive is ready. Thus,

this bit is an inverted copy of the READY input signal

to the 1771 from the disk drive, and is logically ORed

with the *MR signal

6 Record Type/Write Protect

On a Read command, this bit is used in conjunction with

Bit 5 to indicate the type of data address mark that

was read. On a Write command, this bit indicates that

the diskette was write protected.

5 Record Type/Write Fault/Head Loaded

On a Read command, this bit in conjunction with Bit 6

indicates the type of data address mark that was read.

On a Write command, this bit indicates that the write

fault input from the disk drive was detected: it is

thus an inverted copy of the *WF input signal.

On a Restore command, this bit indicates that the

read/write head is loaded against the diskette surface.

This bit is thus the logical AND of the HLD and HLT

signals.

4 Record Not Found/Seek Error

On Read or Write command, this bit indicates that the

desired track and sector were not found.

On a Restore command, this bit indicates that the

designated track could not be verified. This bit is

reset to 0 whenever a new command is loaded.

3 CRC error

On a Read or Write command, if Bit 4 is also set, then

this bit indicates that an error was found in one or

more ID fields; otherwise, it indicates an error in a

data
field.

On a Restore command, this bit indicates that one or

more CRC errors were encountered on a track verification

operation. This bit is reset to 0 whenever a new

command is loaded.

2 Lost Data/Track 00

On a Read or Write command, this bit indicates that

the microprocessor did not respond to the Data Request

(DRQ) within one byte time and that a byte of data was

subsequently lost.

On a Restore command, this bit indicates that the read/

write head is positioned over track 0. This bit is

thus an inverted copy of the *TR00 input to the 1771.

1 Data Request/Index

On a Read or Write command, this bit is a copy of the

DRQ output signal. When set, it indicates that the

Data register is full on a read operation or empty on

a write operation.

On a Restore command, this bit indicates that an index

mark was detected on the diskette. This bit is thus

an inverted copy of the *IP input to the 1771.

0 Busy

When set, this bit indicates that a command is currently

being executed. This bit is reset when a command is

completed and thus indicates that the 1771 is available

to execute another command.

The disk control routine modifies the contents of only the condition code

register.

Finally, note that you can force the drive motor to turn off by writing a

zero into address $FF40. This probably also means you could force the motor

on by writing non-zero there, but the documentation doesn’t explain which

bits to what.

Try visiting:
http://www.rtsi.com/ftparchive.html
ftp://os9archive.rtsi.com/
ftp://maltedmedia.com/coco/
http://www.cloud9tech.com/
http://www.cs.unc.edu/~yakowenk/coco/text/history.html
http://www.vavasour.ca/jeff/trs80.html#coco2
http://vcc6809.bravehost.com/
http://coco.clubltdstudios.com/

There is also a CoCo Web Ring that you should visit
http://m.webring.com/t/TRS-80-Tandy-Color-Computer

Good Luck

Ed