D-Series Syringe Pumps - Isco

D Series Syringe Pumps
Section 6 Serial Interface
There are three types of operation within the network: network
controller, master, and slave. A computer typically serves as the
network controller. It supervises all data flow on the network. It
also polls each unit which initiates data transfer and commands.
Note
The network controller (typically a PC) should not be confused
with the pump controller. The network controller is used in
addition to the pump controller.
The slave unit simply responds to commands accordingly. The D
Series pump functions as a slave unit. These functions may be
combined in one unit; i.e., a computer can function as both a
network controller and a master.
All data transfers are in a frame format. When the network controller
polls an instrument, it will start to respond within 200 ms.
If it does not reply, it will be polled again. If after three attempts
at polling it does not reply, it will be dropped from the polling
rotation. When the instrument does respond, the polling rotation
does not advance until an error-free transfer has occurred.
The frame format for data transfers from the network controller
is as follows:
destination\acknowledgement\message source
\length\message\checksum\[CR]
• The destination is the 1-digit unit identification
number of the instrument to receive the message.
• Acknowledgment is one character to indicate the
success of the previous transmission. There are three
possibilities: (1) E means error, resend the message
immediately (E is sent by the network controller only.
Other units signify errors by not replying; causing the
controller to resend the message). (2) B means busy,
resend message at next poll. (3) R signifies previous
message was received.
• Message source is the unit ID of the unit that originated
the message. If there is no message, this location
is a space (20H).
• Length is the length of the message in 2 digit,
hexadecimal format. Maximum length is 256, with 256
being represented by a 00. This field is eliminated if
there are no messages.
• Message field is the area where the actual information
is located. The maximum length is 256 characters long.
• Checksum is also a 2 digit hexadecimal number. This
number, when added to all the previous characters in
the message (excluding control characters), will result in
a sum. If there are no errors, the result of modulo 256
division of this sum should be 0.
6-6