AW: [sebhc] ET/ETA-3400 ROM-Dump Help

Peter Hofmann peter.hofmann at
Wed Feb 21 12:24:05 CST 2007


Ok. You have two monitor roms: one in the standard et-3400/et-3400a and an
additional one in the expansion box eta-3400.

--> The monitor in the "base unit" contains the main interrupt vectors
(RESET handler, hard- and software interrupt handler) and initializes the
unit after power-up - it generates the "CPU UP" message on the hex-display,
scans the keyboard ... its address range starts at FC00 and ends at FFFF,
which is "1"KB (400H). I wrote F800 for the case, that heath/wintek has
added additional routines(?). The very first ROM 444-17 was a MC6830 mask
rom and later Heath used a 2316 ROM (its an eprom without a uv-window and
has 2KB)?

--> The monitor in the "expansion unit" is used mainly for RS-232 and tape
storage support. Its starting address is 1400 and thats the reason why you
have to start it explicitly with "DO 1400". In case you have connected a pc
to the rs-232 and the parameters (speed,start,stop) are set correctly, you
will see in the terminalemulation the monitor message "MON>". This monitor
is 2KB (800H) long and lies in the address-range 1400-1BFF. At address 1C00
the TinyBasic ROM starts and is also 2KB (800H) long. It fills the range
1C00-23FF. Thats the reason for my interest in the address-range 1400-23FFH.

As you wrote in the former postings the 2 ROMs(444-24/444-25) are the
additionals to the base unit for RS-232/tape and TinyBasic support. Which
function the ROM 444-76 fullfills, I don't know. But never mind ... usually
the part-numbers also "coded in the ROMs" ... I will have to read the dump
and will reverse engineer the dump ... then I will be able to give you more
detailed information ...

I have expressed it wrong (>NOT replace<) - all THREE ROMs are needed !!!
The small 1KB is essential for power-up (shows the power-up message "CPU
UP") and the two others 2KB for RS232/tape/Basic.

You should experiment with it. Connecting the pc + terminal emulation - its
a great event, when you see MON> on the pc-screen. In case you want more
detailed information, should I send it to your email-address, because I
don't know, if the friends in this newsgroup are interested in it?

peter, oe3pha
Vienna, Austria

> -----Ursprüngliche Nachricht-----
> Von: sebhc-bounces at [mailto:sebhc-bounces at]Im Auftrag
> von Paul A. Pennington
> Gesendet am: Mittwoch, 21. Februar 2007 17:49
> An: sebhc at
> Betreff: Re: [sebhc] ET/ETA-3400 ROM-Dump Help
> Peter;
>     A comment and a question:
> > 444-76 ... 2KB NMOS 2316 ROM
> > don't know if monitor/expanded monitor/tinybasic ???
>     This is the monitor in the ET-3400A model.  You are correct
> that it's in
> a 2KB ROM with different pinouts than the 444-76, but I believe
> the code is
> the same, only 1K.  They must move the code up so it ends at
> FFFF, leaving 1
> KB blank at the beginning.  I don't know for sure because my ET-3400A
> doesn't work yet :-(
> > 444-51 ... 2KB NMOS 2316 ROM terminal monitor FANTOM II
> > HEATH/WINTEK - installed in the  expansion box ETA-3400 - U105
>     So you're saying this replaces the standard terminal monitor
> 444-25 in
> the expansion interface?  Was it included with the interface or sold
> separately as an option?
>     Paul Pennington
>     Augusta, Georgia
> --
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