INFICON TM-400 Thin Film Deposition Monitor - Manual (Page 68)

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TM-350/400 Operating Manual
rear panel used for RS-232. The pin layout is shown in Figure 3-7 on page 3-10
and Table 3-4 on page 3-10 lists pin signal assignments, including a definition of
whether the signal is an input or an output of the TM-350/400.
The TM-350/400’s RS-485 port is automatically set up to operate with the following
specifications: 9600 Baud, 8 Bit data, No Parity, 1 Stop bit
10.4 IEEE-488 Parallel Interface
The optional IEEE-488 interface provides the TM-350/400 with the ability to
communicate with computers and other devices over a standard IEEE-488
interface bus. The IEEE-488 interface, also known as GPIB or HPIB, provides an
eight bit parallel asynchronous interface between up to 15 individual devices on the
same bus. This means that one computer equipped with an IEEE-488 interface
card can communicate with up to 14 TM monitors or other devices.
The pin layout of the IEEE-488 port is shown in Figure 3-6 on page 3-9 and Table
3-3 on page 3-9 lists pin signal assignments, including a definition of whether the
signal is an input or an output of the TM.
The RS-232 serial port can still be used with IEEE-488 installed. However, since
both interfaces use the same input and output message buffers, they should not be
used at the same time. This will result in communication errors.
10.5 Protocol
All communications between the computer and the TM-350/400 are in the form of
message character strings with the format:
* Two byte header - (FFh, FEh i.e. Chr$(255), Chr$(254)) The header indicates the
beginning of a message.
*One byte device address - (0 to 32) The device address byte defines the bus
address of the instrument that sent or should receive the message. The device
address will range from 0 to 32. See
section 4.3.2 on page 4-5 for instructions on
setting the TM's device address. A message sent to a device address of zero will
be received by all TMs except in the case of the IEEE-488 interface. With this
interface, only the addressed device will receive the message.
*One byte instruction code - (0 to 6) Defines the code number of the message.
*One byte message length - (0 to 249) Indicates the number of data bytes
contained in the message.
* One byte checksum - (0 to 255) The checksum byte is used for transmission error
detection. If the TM receives a message with an incorrect checksum, it will
disregard the message. The checksum is the compliment of the one-byte sum of
all bytes from, and including, the instruction code to the end of the message. If the
one-byte sum of all these bytes is added to the checksum, the result should equal
255.