SMC FD37C65B and revision C Errata sheets?

Holm Tiffe holm at
Sun Dec 19 15:22:16 CST 2021

Hi all,

the german Engeneer Tillman Reh has build an Zilog Z280 SBC card with
Eurocard Bus connector:
The Software is open and Tillman allows the PCB to be reproduced from
his original Gerber files on request.

Unfortunately some parts for those cards are almost unobtanium in the
meantime, the Zigzag DRAMs, the COM8117 Uart, the LT1134 Driver chip
and also the SMC FD37C65CLJP FDC are difficult to source.
I have two such cards and I got all the necessary parts, but I have
friends that are also interested in such a card to run CP/M 3 or UZI280
on that Z280 (The Z800!) 16 Bit CPU.

There are many other FDCs that should be compatible, the WD37C65 for
example. This was used in many PC related Floppy controllers..but they
are in fact not compatible. The use of the SMC37C65CLJ P  seems to be
necesary for this board, for reasons that are unclear.

While copying data to the disc there happens a timeout on the earlier
FDC varaints, I have read somewhere that reading the status register
gives unexpected results, they have tried to fix this already in the
90ies by inserting some delays, w/o success.

Has someone here Errata Sheets for those SMC FD37C65B (not working) and
FDC37C65C (working) variants of that FDC Chip, so that one can see what
they may have changed between the releases?

Here are some part of the BIOS:

; I/O-Page mu~ bereits auf BOARDP gesetzt sein. Ver{ndert ABHL.

    if loader
        ld      hl,CList
        ld      hl,(CmdAdr)     ; Zeiger auf Befehlsliste
FdcCo1::in      a,(FdcSta)      ; (Einsprung mit Zeiger in HL)
        jr      nc,FdcCo1       ; warten bis FDC-RQM (Request for Master)
        jr      c,FdcErr        ; bei falscher Datenrichtung: DIO-Error
        ld      a,(hl)
        out     (FdcDat),a      ; Befehls/Datenbyte an FDC ausgeben
        inc     hl              ; Zeiger auf naechstes Byte
        djnz    FdcCo1          ; alle Befehlsbytes ausgeben

; DIO-Error (Datenrichtungsfehler im FDC) : Stoppen des Systems
;*** evtl. Fehler korrigieren und weiterarbeiten?
; (Ist Fehler ueberhaupt korrigierbar?)

FdcErr: ld      hl,DioMsg
        call    PMsg            ; "DIO-Error" ausgeben
        halt                    ; sicherheitshalber nicht weiter arbeiten

It seems that the FDC Status register requests a data transfer in the
wrong direction on the B-Release Chips... It is this "DIO-Error" that
happens after a few write operations, but formating the disk is possible.

Kind Regards,


       Technik Service u. Handel Tiffe,, Holm Tiffe, 
         Goethestrasse 15, 09569 Oederan, USt-Id: DE253710583
info at Fax +49 37292 709779 Tel +49 37292 709778 Mobil: 0172 8790 741

More information about the cctalk mailing list