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Problem reading binary data from CR11 card reader


Experienced Member
Apr 3, 2008
I've been messing around with reading punched cards from a CR11 under SIMH on a PDP-11/04 running RT-11 V5.3.

With the help of the card-file translation tools written by Doug Jones, I'm able to read-in a short BASIC program (consisting of 4 cards) after configuring the CR driver (in RT-11) with the command "SET CR NOIMAGE,TRIM". By that I mean that when I run the RT-11 command "COPY CR: TT:", the entire BASIC program displays on screen. I can do this both using a "card input file" generated using Doug Jones' translation tool, or by using a simple ASCII file as the input card file. Similarly, I can COPY from the CR device to a file, rather than to device TT.

But I also want to be able to read-in binary (12-bit) data from the punched cards. RT-11 provides a setting for this ("SET CR IMAGE"), which I've tried with both TRIM and NOTRIM options. When I try this, the COPY operation completes but all I get is a stream of NULs. I've tried all potentially relevant switches for both the COPY and the PIP commands, with no luck so far.

Perhaps the problem is that the CR driver can only pass 8-bit bytes (rather than 12-bit binary data)?

Does anyone recall whether it should be possible to access binary card data through the CR driver (eg using the CR device), or was it always necessary to do direct I/O to the CR11 controller in order to recover binary data?