OKI ML3390 01091308*01256402 User Manual

D-29

Appendix D: Interface Data

Maximum length of block: 0 to 1 KByte (8 KByte)

The maximum length of a block of data equals the capacity of the
interface’s printer buffer. This capacity should not exceed 1 KByte.

If a parity error occurs or if the buffer overflows during the trans-
mission, the block causing the error is ignored, a NAK signal is sent
and the block is requested again.

Please note that closed loops are created when using a current loop
interface in order to connect the sender (host) to the receiver (print-
er).

Connections with one or more current loops can also be produced.
If only one current loop is used, only the blocked Centronics
Blocked Duplex transmission protocol can be used. When using
only one circuit, the receiving and sending circuit of the host and
printer must be connected in series. It is therefore not possible to
receive print data and send status messages simultaneously. Each
current loop has to contain a power source which can be made
available by either the host or the printer. Several power sources are
not allowed within one loop.

Only example circuits are listed below as it is not possible to show
the numerous Current Loop interfaces with the different circuits.
The required printer configuration is explained in detail.

As an example, the connection of the IBM Asynchronous Commu-
nication Adapter to the Current Loop interface of the printer is de-
scribed. With this adapter the operating mode can be set to RS-232C
interface or Current Loop interface. For further information about
the configuration of this adapter see IBM Personal Computer Techni-
cal Reference Manual, P/N 6936844,.