Zilog Brain Dead:
things best forgotten

You'd think that Exxon information systems
would be the best at using their own chip.
Nope! No way!

Zilog's MCZ1 and MCZ2 Z80 systems went nowhere!
  1. proprietory backplane/bus
  2. Their preferred DOS was RIO, RIO/CP
  3. Their PLZ programming language (not to be confused with PL/M or PL/I)
  4. Z-net Ethernet based network
  5. Herb Johnson chronicles his struggles with his Zilog MCZ 1/20 Z80 system 


    *** Zilog Brain Dead

Anyone who works with Zilog products says that with affection :-)

- the TRS-80 "Trash DOS"
[ one of many proprietory dead-end systems/environments ]


- RE TI
[ Z8000 ZEUS / URTS + System V ]

bus snooping for "RE TI"

Return from Interrupt Cycle  ED / 4D (RETI)
https://www.zilog.com/docs/z80/um0081.pdf
When several Z80 peripheral chips are in the daisy-chain,
IEI becomes active on the chip currently under service
when an EDH Op Code is decoded.
If the following Op Code is 4DH,
the peripheral being serviced is re-initialized and its IEO becomes active


    *** not just CP/M
MP/M
TRASH-DOS
Xinu
UZI


https://www.quora.com/Why-hasnt-a-language-as-powerful-as-C-C++-or-Java-been-made-with-easier-syntax

Les Morton

Worked at Morton Word Processing9y

Why haven't a language as powerful as C/C++ or Java been made with easier syntax?

Well back in the 1980s, there was.
Zilog developed a 'high-level' language called PLZ/SYS
which was Pascal/Algol like in its syntax.
They also had a language called PLZ/ASM which was
syntactically similar to PLZ/SYS,
but aimed at assembly language programmers.
It was basically a macro-pre-processor
which meant that you could code assembly language in a higher-level way.
It obviously didn't catch on and only ever ran on the
Zilog RIO operating system on Z80 processors.
This was when most Z80 computers were running CP/M,
so it was a minor language running on a minor OS.
I did a lot of coding in PLZ/SYS, not so much in PLZ/ASM.