Modes 1-6 & 8.
PSI BOX Reference
Figure 6-2 HPGL Output Commands.
_________________________________
OA
Output Actual.
OC
Output Coordinates.
OD
Output Digitised Point.
OE
Output Error.
OI
Output Identity.
OP
Output P1 And P2.
OS
Output Status.
OW
Output Window.
The talk back facility of Mode 8 allows the plotter to
receive all these output commands and reply to them. When the
PSI BOX RS232 input buffer is empty, the PSI BOX polls the
plotter for a response to the computers request after every three
second period of inactivity on the RS232 bus. This mechanism
allows any data waiting in the plotter buffer to be correctly
received by the computer within a short time of it becoming
available.
3)
HPGL RS232 Interface Flow Control Commands.
__
______________________________________________________
Whilst the plotting and output commands that the two
plotters understand are identical the RS232 plotter also responds
to several FLOW CONTROL commands that are absent from
IEEE plotters. These Flow Control commands regulate the
transfer of information along the RS232 interface between the
computer and the plotter. Thus the computer can clear the
plotters buffer, request the plotter reply with the size of the
plotters, return an error status and set the output mode of data
between the plotter and the computer. IEEE plotters do not
require these functions but software packages driving RS232
plotters may expect the plotter to behave as if it does have them.
Mode 8 of the PSI BOX allows any IEEE plotter to completely
emulate the Flow Control of an RS232 plotter.
The Flow Control commands are three byte commands that all
start with the ESCAPE character, decimal 27 followed by the
decimal point character. The third character identifies the specific
flow control function. Depending on the command, various
Chapter 6
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