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Here is some notes that i found. NOTES: 1. FRAME is set to 0FF to indicate completion of service request. 2. All IOCB's are allocated as required. 3. IOCB OFFSETs are 00-IOCB0 .... 70-IOCB7, if the IOCB OFFSET is specified as 0FF, then the next free IOCB will be assigned, and the assigned offset will be returned in FCOMD. 4. Return STATUS is 01 to indicate success, any other code indicates some form of error (negative) or warning (positive). 5. The X and Y registers and the accumulator are set to the call values before an execute frame and the values after the execution are returned in the call frame. 6. The minimum transfer is 1 byte the maximum transfer is 1024 bytes, except for OS STD frames for which the maximum is 128 bytes. 7. Atari memory area 2000-38FF is available for CPM users. 8. For DISK type OS calls, the byte count is ignored before execution, all disk transfers are one sector at a time. The byte count, after reads, contains the number of bytes actually in that sector. 9. FX will be set to the value of the CH (KEY) register for STD-OS calls, a value of FF indicates no key depressed. 10. For Status Commands on output devices, a FSTAT return of 01 implies that the device can accept a character. The DEV STATUS bytes will only be valid if the Device Code is not set for immediate return.
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Atari XF551 floppy driver / power switch
sup8pdct replied to macsonny's topic in Atari 8-Bit Computers
Sounds like timing isn't right or sio in or out isn't quite right in some way when you get the Squirt sound The crystal also affects sio timeing. It can be a little out but beyond a limit, strange things happen. One thing it could be is the highest address line from the 8040 not connecting properly, unlikely but you never know. Latest std rom is 7.7 If you can, boot dos with another drive, then try a status command or percom read or write block with drive you are having trouble with when drive switches are set to squirt position. use std atari rom. -
Atari XF551 floppy driver / power switch
sup8pdct replied to macsonny's topic in Atari 8-Bit Computers
1st question i would ask is what voltage is going to the 5v regulator??