TMA-11 Read

Hi, I am trying to archive my tapes. I am having difficulty reading the tapes. I tried 2 tapes that are of low importance. I am able to read the first 2 records (the first record is 14 bytes and the second record is 512 bytes). I see the tape move for the read as well as the backspace operations. I setup a simulated environment to test prior to using real hardware. Using a slightly modified version of SIMH along with PDP11GUI and a virtual tape, I successfully read virtual tapes. Now that everything is working on a simulator, I am using the same code on real hardware. The real hardware is a PDP-11/10 with 32kw core memory, TMA-11 controller with TS03 tape drive. I also have a RK-11 controller with an attached RK05j drive which is available, but is not used during this scenario. I don't know the actual format of the tape. My goal is to get a binary copy of the tape suitable for use with SIMH. Now that I am using real hardware, I am getting a Record Length Error. I set the read buffer to 2048 bytes (1024 words). The values I have from the TMA-11 registers is as follows: MTS 001105 MTC 160202 MTBRC 000000 MTCMA 000000 MTD 000000 MTRD 000000 I am looking for some source code to figure out what is going wrong. I have reviewed the simple example in the TMA-11 documentation, but proper error handling is not performed. Thanks! ; +=============================================================== ; | read ; +=============================================================== ; | ; | Read record from tape. When an EOF is detected, 'rsize' is ; | set to 0. When the second EOF is detected (ie. end of tape) ; | 'exit' is set to TRUE. ; | ; | On Entry: ; | rsize has the number of bytes in the buffer ; | ; | On Exit: ; | all registers unchanged ; +--------------------------------------------------------------- read: mov #MAXTRIES, @#retries ; maximum number of retries retry: tstb @#MTC ; is controller available? bpl retry ; no, wait for controller 1$: bit #MTATUR,@#MTS ; is tape unit ready? beq 1$ ; no, wait for tape unit dec @#retries ; bpl 2$ ; retry halt ; too many reties (bails out here) 2$: mov #rbuf, @#MTCMA ; read buffer (buffer begins at end of code) mov #174000, @#MTBRC ; max buffer size (2048 bytes) mov #60003, @#MTC ; unit #0, 800bpi, read, go 3$: tstb @#MTC ; is read complete? bpl 3$ ; no, wait for completion mov @#MTS, R3 mov @#MTC, R4 mov #0, @#rsize ; assume EOF reached bit #MTAEOF,@#MTS ; did we hit EOF? (MTAEOF is 040000 bne done ; yes, so we are done tst @#MTC ; error? bpl 5$ ; no error mov #-1, @#MTBRC ; number of records to backspace mov #60013, @#MTC ; unit #0, 800bpi, read, go 4$: tstb @#MTC ; is backspace complete? bpl 4$ ; no, wait for completion br retry ; try read again 5$: mov @#MTCMA,@#rsize ; determine number bytes read sub #rbuf,@#rsize done: inc @#reccnt ; another record (or EOF) rts pc