INFICON STM-2 USB Thin Film Rate/Thickness Monitor User Manual

Page 70

5 - 2

STM-2 Operating Manual

ADDR. . . . . . . . . . . . . . . . . . . . . . . . One byte address field

The address (ADDR) byte identifies the
SMDP address in order to select which
device the command/query is sent to.

NOTE: Slave address is defaulted to 16.

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 5.2.1.2

but the RSP2 through RSP0 field will be
non-zero (indicating actual unit response
status) (see

section 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

CMD3 CMD2 CMD1 CMD0 RSPF RSP2 RSP1 RSP0