DC319 DLARTs and T11s (was T-11 ....)

Paul Koning Paul_Koning at Dell.com
Fri Jan 16 09:56:05 CST 2009

>>>>> "Bob" == Bob Armstrong <bob at jfcl.com> writes:

 Bob> If you can't find a DC319, then the alternative is to build a
 Bob> DL11 compatible interface using a standard UART like the 6402
 Bob> and a handful of discrete logic.  I think the minimum you could
 Bob> get away with would be to implement the DONE and INTERRUPT
 Bob> ENABLE bits (bits 6 and 7) for both the receiver and transmitter
 Bob> CSR, and then to implement the standard vectors at 60/64.  Oh,
 Bob> and of course the data registers for the transmitter and
 Bob> receiver.

 Bob> The KL11 also implements a MAINTENANCE bit, a BUSY bit, and a
 Bob> READER ENABLE bit, but a) we have no reader, b) I doubt (I'm
 Bob> hoping) much software ever looks at the BUSY bit, and c)
 Bob> probably nothing uses the MAINTENANCE bit except the
 Bob> diagnostics.

 Bob> ISTR that DEC had an "official" standard written down for
 Bob> exactly what was required of a DL-11 compatible serial
 Bob> interface, but I can't find it anywhere.

The approach you described should do the job.  If all you need is
compatibility with console boot drivers, you could leave off the
interrupt machinery since those things tend to run in polled mode.
But for an OS you'd need IE and the interrupt.  And if you want to
ignore inbound errors, you need only implement the low byte of the
receive data register.

This would be a nice small VHDL exercise...


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