Stop Bits; Transmission Errors - HP 7470A Interfacing And Programming Manual
Graphics plotter
Hide thumbs
Also See for 7470A:
- Operator's manual (41 pages) ,
- Interfacing and programming manual (114 pages) ,
- Service manual (141 pages)
Table of Contents
Advertisement
4. The clock pulse must be a logic on of +2 V < V < 25 V and a logic off
of -25 V < V < +0.8 V (3.5kfl input impedance).
5. Care should be taken to keep the transmission lines as short as
possible to minimize transmission line reflection noise.
Stop Bits
The plotter is configured to automatically verify or generate one or two
stop bits, depending on the setting of the plotter's baud rate switches.
Refer to the 7470A Operator's Manual for more information.
Transmission Errors
Transmission errors occur when communication between the computer
and plotter is incomplete or does not conform to what is expected or
required by either party.
Transmission errors include:
0 Framing error —the plotter does not detect a valid stop bit at the end
of every character.
0 Parity error — the plotter does not detect the expected parity (odd or
even).
0 Overrun error —a plotter instruction writes over another instruction.
0 Buffer overflow error —the plotter receives more bytes of data than it
has space for in the buffer.
When the plotter detects a framing, parity, or overrun error, it turns on
the front panel ERROR light and sets error code 15. This error code
generally indicates that the communication incompatibility is hardware
related (incorrect stop bit jumper installation, wrong parity selection,
incompatible or incorrectly set baud rates, etc.).
When the plotter detects a buffer overflow, it turns on the front panel
ERROR light and sets error code 16. The last HP—GL data that caused the
overflow will be lost. Error code 16 generally indicates an improperly
established handshake protocol.
The ERROR l ight remains on until either the user interrogates the plotter
via an output extended error command, ESC . E, and the plotter re
sponds with the appropriate error code, or the user turns the plotter off,
or an HP—GL initialization instruction, IN, is processed, or a front—panel
reset occurs.
A complete list of error codes is included with the discussion of the
ESC . E instruction.
RS-232—C/CCITTV.24 INTERFACING
10-13
Advertisement
Table of Contents
