Table of Contents
Advertisement
CABLE ADAPTER
The cable adapter is the hardware (drivers, receivers,
and logic) on the planar board that handles the incoming
and outgoing communications between the controller
and the printer.
Note: The 5256 is attached to the controller by a twinaxial
cable. See Cabling Locations (108), and Cable Thru in the
Features section of this manual.
Frame Concept
Communications between the controller and the cable
adapter at the printer are carried by 16-bit frames that
are transmitted to and from the controller on an
as-required basis. The cable carries no signal between
frames. To understand what is to follow, it is necessary
to explain briefly the phase encoding used for sending
data on the system cable. The data is phase encoded
so that a transition occurs during each bit time (a 0 to 1
transition for a 0 and a 1 to 0 transition for a 1). If no
transition occurs during a bit time, a code violation has
occurred. Because the transition divides the bit into 2
parts, the term half bit will be used in the explanation
that follows. (The data sent on the system cable is a
4-level signal. Refer to the system documentation for a
further explanation of the phase encoding process.)
When information is to be sent on the cable a group of
five 1 bits (1010101010 half bits) is sent to establish bit
synchronization. Immediately after the 1 bits, a group of
3 half bit l' sand 3 half bit C's is sent to establish
frame synchronization.
After the frame synchronization half bits, the frame is
sent, starting with the sync bit.
The transmission rate is 1.0 MHz (16
microseconds per frame). The frame bit assignment
during transmit and receive operations is shown in the
following diagram:
4-6
Advertisement
Table of Contents
