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Tandy Portable Disk
Drive
(PDD1 and PDD2)
Command Reference
General Reference
All commands are in a request/return format (half-duplex)
General request format:
preamble type length data checksum
General return format:
type length data checksum
(all values are in HEX)
| command | request | return |
|---|---|---|
| directory ref | 00 | 11 12 |
| open file | 01 | 12 |
| close file | 02 | 12 |
| read file | 03 | 10 12 |
| write file | 04 | 12 |
| delete file | 05 | 12 |
| format disk | 06 * | 12 |
| drive status | 07 * | 12 |
| drive condition | 0C * | 15 |
| rename file | 0D | 12 |
* PDD2 treats the disk as two banks of 100k each. All commands except these two must specify the bank number as part of the request. The above commands reference BANK 0. To reference BANK 1 you must add 40 HEX to these values (bit 6 = bank number). E.G. 'open file' becomes 41 for BANK 1.
| Type 00 - Directory Reference 2 1 1 24 1 1 1 bytes +----+--+--+--------------+----------+------------+------+ |5a5a|00|1a| filename |attribute |search form |chksum| +----+--+--+--------------+----------+------------+------+ Preamble - always 'ZZ'
checksum - see below for calculating |
| Type 01 - Open file 2 1 1 1 1 bytes +----+--+--+------+------+ |5a5a|01|01| mode |chksum| +----+--+--+------+------+ Preamble - always 'ZZ'
checksum - see below for calculating |
| Type 02 - Close file 2 1 1 1 bytes +----+--+--+------+ |5a5a|02|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 03 - Read file2 1 1 1 bytes +----+--+--+------+ |5a5a|03|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 04 - Write file2 1 1 1-128 1 bytes +----+--+---+------+------+ |5a5a|04|01-|data |chksum| | | | 80| | | +----+--+---+------+------+ Preamble - always 'ZZ' |
Type 05 - Delete file2 1 1 1 bytes +----+--+--+------+ |5a5a|05|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 06 - Format Disk2 1 1 1 bytes +----+--+--+------+ |5a5a|06|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 07 - Drive Status2 1 1 1 bytes +----+--+--+------+ |5a5a|07|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 0C - Drive Condition 2 1 1 1 bytes +----+--+--+------+ |5a5a|0C|00|chksum| +----+--+--+------+ Preamble - always 'ZZ' |
Type 0D - Rename file 2 1 1 24 1 1 bytes +----+--+--+-------+------+------+ |5a5a|0D|19|newname|attrib|chksum| +----+--+--+-------+------+------+ Preamble - always 'ZZ' |
Type 10 - Read file Return 1 1 0-128 1 bytes +--+---+----------+-----+ |10|00-| file data|cksum| | | 80| |cksum| +--+---+----------+-----+ return - type 10
file data - data read from file |
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Type 11 - Directory reference return 1 1 24 1 2 1 1 bytes +--+--+--------+------+----+----+-----+ |11|1c|filename|attrib|size|free|cksum| +--+--+--------+------+----+----+-----+ return - type 11h |
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| Type 12 - Normal Return 1 1 1 1 bytes +--+--+-----+-----+ |12|01|error|cksum| +--+--+-----+-----+ return - type 12h
checksum - see below for calculating |
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Type 15 - Drive Condition Return 1 1 1 1 bytes +--+--+---------+-----+ |15|01|condition|cksum| +--+--+---------+-----+ return - type 15h 7 6 5 4 3 2 1 0 bit
+-+-+-+-+-+-+-+-+
MSB |0|0|0|0|x|x|x|x| LSB
+-+-+-+-+-+-+-+-+
| | | |
| | | +--power (0=normal 1=low)
| | +----write protect (0=not prot 1=prot)
| +------disk out (0=disk in 1=disk out)
+--------disk change status (0=not changed 1=changed)
checksum - see below for calculating |
| Get directory | req 00 search form 01 req 00 search form 02 (repeat as needed) |
| Write file | req 00 search form 00 req 01 mode 01 or 02 req 04 (repeat as needed) req 02 |
| Read file | req 00 search form 00 req 01 mode 03 req 03 (repeat as needed) req 02 |
| Rename file | req 00 search form 00 req 0d |
| Delete file | req 00 search form 00 req 05 |
The check sum is "the one's complement of the least significant byte of the number of bytes from the block format through the data block". Most people (me included) don't understand what that involves if you have to calculate it. Fortunately I found an example of how to do this and so I'm passing it on to you.
Checksum=(bytes MOD 256) XOR 255
where bytes = number of bytes including the Request Type, Length and all Data fields (but not including the preamble).
A lot of the above commands can be set up in advance since there is no variable part to calculate. Some commands must have the length and checksum calculate as the data is built but the others don't. Here's how I set up some of the commands in my program:
Close$="ZZ"+Chr$(2)+Chr$(0)+Chr$(253)
Dir1$="ZZ"+Chr$(0)+Chr$(26)+Space$(24)+"F"+Chr$(1)+Chr$(158)
Dir2$="ZZ"+Chr$(0)+Chr$(26)+Space$(24)+"F"+Chr$(2)+Chr$(157)
Status$="ZZ"+Chr$(7)+Chr$(0)+Chr$(248)+Chr$(13)
Format$="ZZ"+Chr$(6)+Chr$(0)+Chr$(249)+Chr$(13)
Erase$="ZZ"+Chr$(5)+Chr$(0)+Chr$(250)
Seek$(1)="ZZ"+Chr$(1)+Chr$(1)+Chr$(1)+Chr$(252)
Seek$(2)="ZZ"+Chr$(1)+Chr$(1)+Chr$(2)+Chr$(251)
Seek$(3)="ZZ"+Chr$(1)+Chr$(1)+Chr$(3)+Chr$(250)
The above commands can be sent directly without any calculating to speed up your program.