Model 574 Programmable Counting System (PCS)
116 - GSE Scale Systems
will abort the print request. If none of the four
transmissions are set for "onrq2", then when <PRINT>
is pressed, all transmissions which are set for "onreq"
will be sent. In effect, selecting P220.04 gives the
operator the choice of which transmission to send.
P221.XX Port
This parameter selects whether the 2nd Custom Transmit
will be sent out through the Print or Comm Port.
P222.XX Mot'n
This parameter enables or disables motion delay on the
2nd Custom Transmit. The selection of this parameter
applies to all selections for P220 above except for
P220.03.
Parameters P230 to P232 and P240 to P242
deal with the 3rd and 4th Custom Transmits in the same
manner as described for the 2nd Custom Transmit in
P220 to P222 above.
15.5 Communications (Receive)
Operations
Any command that the Model 574 is capable of
executing can be sent in from a remote source via a
serial, asynchronous RS-232 communciation link.
Application uses for this capability include barcode input
of data, host computer interfacing and the transmission
of setup files directly into the instrument. (Also refer to
chapter 28, Parameter Download and Upload).
COMMAND LANGUAGE
The command language used by the instrument is based
upon use of the percent (%) character. Any character
received after a percent character is treated as a
command, provided it is a recognized code. Any invalid
commands that are received are ignored. Lower case
characters are used for the commands which represent
keys on the 574 front panel. Capital letters and a few
other characters are used for commands designed
primarily for use within Macros. (The instrument %
command character is similar in nature to "ESCape"
codes used to program printers).
Table 15 shows a listing of RS-232 Keyboard
Commands used to simulate the front panel keys.
Additional commands are available as described in
Chapter 16 on Macro Programming Operations, however
the branching Macro commands are not designed to be
executed via RS-232 input and will not perform any
useful function.
If an entry is in process and a carriage return is received,
then the entry is cleared. Otherwise the carriage return
does not affect the operation of the instrument. However,
every carriage return that is received is counted by the
instrument as a means of tracking down errors.
Commands may also be sent to the instrument as single 8
bit characters which is the character with the high bit set.
Sending these extended ASCII codes is not normally
necessary and it is better to simply send the "%"
character followed by the appropriate command.
RECEIVING DATA
The 574 has a 256 byte received data buffer. When
characters are received, they are stored in this buffer
until the instrument has a chance to process the received
data. When the buffer has 240 characters buffered,
leaving room for only 16 more, the instrument will de-
assert its handshake output, as specified by setup
parameter P204. In other words, the 574 will transmit an
XOFF character and / or change the level of its CTS
output to -12V. RTS is LOW (-12V) when not ready to
receive data. The RTS is HIGH (+12V) ready to receive
data (when transmitting). If the transmitting device
continues to send more than 16 characters after the 574's
handshake output has been de-asserted then characters
may be lost. This situation constitutes an over-run error
and is indicated by the message ovrun error.
As soon as the available room in the data receive buffer
increases to at least 24 characters, the unit re-asserts its
handshake outputs, informing the transmitting device
that it is OK to resume transmitting. Note however that
NOTE:
If multiple transmissions are established and some,
but not all are to be motion delayed, then the last
one(s) should be motion delayed. If the first is
motion delayed, the subsequent transmissions will
all be motion delayed also, regardless of their setup
selections.
NOTE:
P201 must be set to 8 bits in order for this feature to
work properly.
To Next Page
Loading...