INFICON STM-2XM 2-Channel Rate/Thickness Monitor - Manual (Page 87)

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STM-2XM Operating Manual
ADDR . . . . . . . . . . . . . . . . . . . . . . . . One byte address field
The address (ADDR) byte identifies the
SMDP address (refer to
section 3.2.1.2 on
page 3-10 ) in order to select which device the
command/query is sent to.
NOTE: RS-485 communication limits the
number of attached devices to 32.
Each connected instrument must be
assigned a unique address. The
slave reply repeats the address
when it replies to the master,
verifying the address of the
instrument receiving the command.
The range of values are 10 hexadecimal to
FE hexadecimal (16 to 254 decimal).
Address FF hexadecimal is reserved. It is
used as an extension to indicate another byte
of address information follows for products
that have an address range higher than an
address of FE hexadecimal.
CMD_RSP . . . . . . . . . . . . . . . . . . . . Command/Response field
When a command is sent from master to
slave, the RSPF bit is zero and the RSP field
(3 bits) is zero.
When a command is received from a slave to
a master, CMD bits are the same as in the
message that was sent (see
section
5.5.2.1.2 ), but the RSP2 through RSP0 field
will be non-zero (indicating actual unit
response status) (see
section 5.5.2.1.3 ). The
slave will set or clear the RSPF flag bit in the
reply CMD_RSP frame to indicate an
unacknowledged slave reset. This bit only
has meaning when a command is going from
slave to master. If this bit is 1, the slave has
been reset since the last AckPF,
acknowledge power fail, flag command was
received (see
Table 5-1 ).
Table 5-1 Command/Response
D7 D6 D5 D4 D3 D2 D1 D0
CMD3 CMD2 CMD1 CMD0 RSPF RSP2 RSP1 RSP0