MKS Stabil-Ion 370 Series, Instruction Manual, Page: 90 / 122

4 Preparing the Stabil-Ion System for Operation
4-32
Series 370 Stabil-Ion Instruction Manual - 370119
3. After holding the SET button in for about 5 seconds, the setpoint will scroll until the button is
released. It will scroll slowly until a decade boundary is crossed and then will speed up to
facilitate rapid changes across many decades. Release the button when you have entered the
desired decade, and then depress it again to scroll slowly within the decade to reach the
required setpoint.
After the setpoint button is released, the display will return to pressure data after 2 seconds. At this
time the new setpoint will be stored in non-volatile memory and will not change when the
Controller is turned OFF.
4.12 Preparing for use of the RS-232 Computer Interface
For set up instructions see Section 2.1.4 on page 2-8.
For connection instructions see Section 3.8 on page 3-13.
Check the user's manual for the host computer to be sure the protocol used is compatible with that
established via the switch configuration in the RS-232 module.
Communication with the Control Unit is via ASCII strings. A message consists of a command and a
command modifier, followed by a terminator. The message may contain leading spaces, and the
command and modifier may be optionally separated by spaces or commas. No spaces may appear
within the command or the modifier, only between them.
The terminator expected by the Control Unit is an ASCII carriage-return line-feed, denoted here by
CRLF. The carriage-return is optional, and messages terminated with only the line-feed will be
accepted. Note that the CRLF terminator is appended automatically by the host computer's
interface software to the message string supplied by the user.
If extra characters are found in the message after it has been successfully interpreted but before the
terminator, they will be ignored. Characters can be upper- or lower-case. All messages to 370 will
receive a reply, consisting of an ASCII string of numbers and upper-case letters terminated with
CRLF. Pressures will be returned in the format X.XXE
±
XX.
4.13 Preparing for use of the RS-485 Computer Interface
The Series 370 Controller uses a command-response half-duplex protocol. If the controller
recognizes received data as a valid command, it will check the command string address and
compare with its own. If the addresses match, the controller will process the command and then
respond. In all configurations, only one twisted pair will have data transmissions in one direction at
any time. The timing of the data transfer is shown in Figure 4-20 below. T0 is 10-13 mS + 10 bit
times with S2.1 in the OFF position, T0 is greater than 700 microseconds with S2.1 in the ON
position, and T1 is greater than 300 microseconds. Adhering to these timing constraints will ensure
data is not overwritten.