Specifications

Special Memory (SM) Bits
C-7
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
Table C-11 Special Memory Byte SMB30
Port 0
Port 1 Description
Format of
SMB30
Format of
SMB130
7
MSB LSB
Freeport mode control byte
ppdbbbmm
0
SM30.6
and
SM30.7
SM130.6
and
SM130.7
pp Parity select
00 = no parity
01 = even parity
10 = no parity
11 = odd parity
SM30.5 SM130.5 d Data bits per character
0 = 8 bits per character
1 = 7 bits per character
SM30.2 to
SM30.4
SM130.2
to
SM130.4
bbb Freeport Baud rate
000 = 38,400 baud
001 = 19,200 baud
010 = 9,600 baud
011 = 4,800 baud
100 = 2,400 baud
101 = 1,200 baud
110 = 600 baud
111 = 300 baud
SM30.0
and
SM30.1
SM130.0
and
SM130.1
mm Protocol selection
00 = Point-to-Point Interface protocol (PPI/slave mode)
01 = Freeport protocol
10 = PPI/master mode
11 = Reserved (defaults to PPI/slave mode)
Note: When you select code mm = 10 (PPI master), the PLC will
become a master on the network and allow the NETR and
NETW instructions to be executed. Bits 2 through 7 are ignored
in PPI modes.
SMB31 and SMW32: Permanent Memory (EEPROM) Write Control
You can save a value stored in V memory to permanent memory (EEPROM) under
the control of your program. To do this, load the address of the location to be
saved in SMW32. Then, load SMB31 with the command to save the value. Once
you have loaded the command to save the value, you do not change the value in V
memory until the CPU resets SM31.7, indicating that the save operation is
complete.
At the end of each scan, the CPU checks to see if a command to save a value to
permanent memory was issued. If the command was issued, the specified value is
saved to permanent memory.