Oki 320/1 Turbo -- New Serial Interface Card

Oki is employing a new generation of electronics in their dot matrix printers. It's quite a departure from the old stuff, and the serial I/F card has been completely redesigned to work with it. Here's a view of the new card, P/N 44455101.

About all that's on the card is line drivers and receivers. The bulk of the interface circuitry is already resident in the printer's electronics. The card comes with two M3 screws for securing it in place.

By way of comparison, Here's a view of the old 'LXHI' serial I/F card, P/N 55038901.

Following is a list of the Microline models that the new card works with:^[1]

320/1 Turbo Rev I0 and up.
390/1 Turbo Rev H0 and up.
420/1 Rev E0 and up.
490/1 Rev E0 and up.
620/621/690/691.

The loopback test described in this post still applies. All that's changed is that the test now prints out the current serial interface settings, and it no longer reports a RAM test result.

Plugging an old serial I/F card into a current printer does no harm, but the printer won't recognize the old card.

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Oki's RS-232 Implementation

The printer is DTE (Data Terminal Equipment); i.e. the printer's TXD pin is a transmitter, the RXD pin is a receiver. Following are the pin assignments:

Pin 1: Frame Ground -- FG ( i.e. earth/chassis ground).^[2]

Pin 2: Transmit Data -- TXD -- O/P from printer.

Pin 3: Receive Data -- RXD -- I/P to printer.

Pin 4: Request to Send -- RTS -- O/P from printer.

Pin 5: Clear to Send -- CTS -- I/P to printer.

Pin 6: Data Set Ready -- DSR -- I/P to printer.

Pin 7: Signal Ground -- SG (i.e. DC logic ground reference).^[2]

Pin 11: Supervisory Send Data -- SSD -- O/P from printer.^[3]

Pin 20: Data Terminal Ready -- DTR -- O/P from printer.

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Notes:

[1] Oki's new revision level identification practice is that the last two characters of the serial number give the revision level; e.g. S/N AK16020765I0 is a Rev I0 machine.

The old revision level identification practice was that the fourth character of the serial number (a single alphabetic) gave the revision level; e.g. S/N 507D1484273 is a Rev D machine.

[2] Oki's practice is to not tie FG to SG within its printers.

[3] SSD appears to be something proprietary to Oki; it's not part of the standard RS-232 interface specification.

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