TU58 tape formatter (was Re: rebuilding DC100A cartridges?)

[Eric Smith]

On Tue, Nov 13, 2018 at 1:47 PM Ethan Dicks via cctalk <
cctalk at classiccmp.org> wrote:

> On Sat, Nov 24, 2012 at 4:08 AM Eric Smith <eric at brouhaha.com> wrote:
> > I spent some time reverse-engineering the firmware.  There is only one
> > undocumented opcode, decimal 10, and I haven't yet figured out what it
> > does, but it definitely doesn't format a tape.
>
> Is Opcode #10 the "Enter MRSP Mode" or is that something else?
>

I'm still not sure what it does, but it was present in the early 23-089e2
firmware, and gone (acts as no-op) in the later 23-294e2 and 23-389e2
firmware versions.

MRSP mode requires a command 12 (hexadecimal?) according to this page:
    http://www.willsworks.net/pdp-11/tu58-emu
but neither the 23-089e2 nor 23-389e2 firmware seem to include that. I
haven't checked 23-294e2.

Maybe there are other firmware versions that include the Enter MRSP
command, or maybe I'm not correctly understanding how the command packet
parsing works in the firmware.