Section 7
Communication Interfaces
This section describes the
two
methods
of
com-
munication between the Model
880
and its host
computer. The communication
can
be
through
either a serial or a
parallel connection. You select
the appropriate type
of
printer/host interface
by
choosing the configuration code while the printer
is
in the menu mode
(see
Section 3).
7.1
DATA
INPUT
BUFFER
All data received by the printer is temporarily
stored in a first-in-first-out
(FIFO) input buffer.
The operational
size
of
the input buffer
is
deter-
mined by the physical
size
of
the buffer installed
(2K bytes standard, 4K bytes or 16K bytes
optional) and the setting
of
configuration code
9C.
To
prevent data from being lost when the printer
receives data at a higher speed than the printer
can print, the printer transmits
"BUSY"
to
the
host. The
"BUSY"
signal stops the host from
sending data. The printer transmits
"READY"
to
the host when more data
can
be
put into the
buffer. The buffer sizes and READY/BUSY points
are shown in Table 7-1.
Table
7-1.
Buffer
Size
and
READY/BUSY
Points
Config.
Code
9C - OFF
Code
9C-ON
2Kbytes
4K
bytes
16K
bytes
Buffer size, serial
256 2048 4096
16384
and parallell/F characters characters characters
characters
BUSY point, 249 1792
3840
16128
seriall/F
only characters characters characters
characters
BUSY point, 256 2048 4096 16384
parallell/F only characters characters characters
characters
READY point, serial
121
1280 2816 15104
and parallell/F
characters
characters characters characters
7-1
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