Compuprint 4247-L03 Programmer Manua - Manual (Page 171)

Appendix B. Interfaces
This section provides technical information for the parallel and serial interfaces.
The Parallel Interface
The parallel interface of this printer fully supports the Centronics protocol plus the specific features
requested by the EPSON and IBM printer connection in monodirectional mode and the Compatibility and
Nibbles modes in bidirectional mode, plus the negotiation phases and the device identifier (as IEEE
P1284).
The parallel interface is available on a specific 36 contact connector type AMPHENOL 57-40360- 12-D56
or equivalent connector for 1284 Type B.
v Drive Capability
Up to 15 feet (5 m) on AWG26 min. wire size of twisted conductors on TTL receiver. The max.
reachable distance is conditioned by the host drive capability and by the noise level along the interface
cable path.
v Printer Connector Type
36 pins, 1284 Type B
v Cable Connector
25 pin, 1284 A Type
Signals Description
According to the IEEE - P1284 Standard, the pins assume different meanings and are identified by
different names depending on the actual handshaking mode as follows:
v Compatibility mode (Centronics)
This lower level mode provides an asynchronous, byte-wide forward (host-to-peripheral) channel with
data and status lines used according to their original definitions. The interfaces power up in the
compatibility Mode Idle phase.
v Nibble Mode
This mode provides an asynchronous, reverse (peripheral-to-host) channel, under control of the host. In
this mode, peripheral device to host data bytes are sent as two sequential, four-bit nibbles using the
four peripheral-to-host status lines. These two modes cannot be active simultaneously.
v Byte Mode
This mode provides an asynchronous, byte-wide reverse (peripheral-to host) channel based on eight
data lines of the interface for data and the control/status lines for handshaking. Byte mode is under host
control and it cannot be simultaneously active with compatibility mode.
Operating Phases
The link protocol is mainly based on the following three phases:
v Negotiation Phase
This phase is activated always by the host, only when in compatibility mode, and defines:
– whether a bidirectional link protocol can be established.
– the handshaking mode as well as the communications mode to be used.
– the device identification, if supported.
v Communication Phase
This phase is based on well defined handshaking rules which depend upon the selected link mode.
v Termination Phase
155