General Interface Operation
17
Data received by the 2553/ 2553E from the IEEE488 interface is placed into a buffer, the
contents of this buffer being acted on when any of the following events occur.
•
The reception of the <NL> character.
•
The reception of any character with the bus EOI line asserted by the controller.
•
The reception of the GET IEEE488.1 bus command.
All whitespace and non-printable characters are discarded prior to being placed into the
buffer, the user may freely use these to improve the readability of commands as desired.
Any lowercase characters (the letters a through z) are converted to uppercase prior to
being placed into the buffer, commands and data may be written in either form, or a
mixture of upper- and lowercase, as desired.
The reception of an empty command, i.e. receiving one of the action events when the
receive buffer is empty, neither causes an error, nor causes any other action.
Multiple commands may be sent at the same time, as a set of commands, by separating
them with the semicolon character, prior to sending one of the action events shown
above. The receive buffer is 512 characters in length. Note that any whitespace
characters are not placed into this buffer, thus are not included in the given length.
Receiving Data from the 2553/ 2553E
The 2553/ 2553E has many thousands of results available to the user, thus it is required
that the user define which of these results is to be read from the 2553/ 2553E prior to
performing a read operation. All data read from the 2553/ 2553E uses the standard 7-bit
ASCII character set. Additionally the data always starts with a <SP> character and
terminates with a <NL> character whenever the IEEE488 bus EOI line is asserted.
To allow the user to predefine several differing sets of data which may be required at
varying times, the 2553/ 2553E uses a “Bank” technique of transmit data buffers. These
banks each have a different transmit buffer and take two forms.
Interrogative Bank
The 2553/ 2553E has one interrogative transmit data buffer. The data placed into this
buffer is defined by specific commands detailed later in this guide. The contents of the
buffer are destroyed when read. If this buffer has data contained within it, then the
transmittal of this buffer’s contents takes priority over any other buffer. In this manner
several status type data may be read from the 2553/ 2553E on the fly without having to
interrupt the normal usage of the transmit buffer banks. This transmit buffer is 256
characters in length, multiple data is separated by the comma character. See the section
on
Reading Status & Settings from the 2553/ 2553E
for details regarding how to use the
transmit buffer.
Summary of Contents for Xitron 2553
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