Libraries
9.2 USS library instructions
S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
417
Table 9- 2 USS_INIT instruction
CALL USS_INIT, Mode, Baud,
Port, Active, Done, Error
The USS_INIT instruction is used to enable and initialize,
or to disable Siemens drive communications. Before any
other USS instruction can be used, the USS_INIT instruc-
tion must be executed without errors. The instruction
completes and the "Done" bit is set immediately, before
continuing to the next instruction.
The instruction is executed on each scan when the "EN" input is on.
Execute the USS_INIT instruction only once for each change in communications state. Use
an edge detection instruction to pulse the "EN" input on. To change the initialization
parameters, execute a new USS_INIT instruction.
Table 9- 3 Parameters for the USS_INIT instruction
VB, IB, QB, MB, SB, SMB, LB, AC, Constant, *VD, *AC, *LD
VD, ID, QD, MD, SD, SMD, LD, Constant, AC *VD, *AC, *LD
I, Q, M, S, SM, T, C, V, L
VB, IB, QB, MB, SB, SMB, LB, AC, *VD, *AC, *LD
Table 9- 4 USS_INIT parameter descriptions
Mode This value selects the communications protocol:
• An input value of 1 assigns the port to USS protocol and enables the protocol.
• An input value of 0 assigns the port to PPI and disables the USS protocol.
Sets the baud rate at 1200, 2400, 4800, 9600, 19200, 38400, 57600, or 115200
Port Sets the physical communication port (0 = RS485 integrated in CPU, 1 = RS485 or
RS232 located on the optional CM01 signal board)
Active Indicates which drives are active. Some drives only support addresses 0 through
Turned on when the USS_INIT instruction completes
Error This output byte contains the result of executing the instruction. The USS protocol
execution error codes (Page 428) define the error conditions that could result from
executing the instruction.
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