Specifications

Special Memory (SM) Bits
C-14
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
Table C-16 Special Memory Bytes SMB86 to SMB94, and SMB186 to SMB194
Port 0 DescriptionPort 1
SMB89 SMB189 End of message character
SMB90
SMB91
SMB190
SMB191
Idle line time period given in milliseconds. The first character received
after idle line time has expired is the start of a new message. SM90
(or SM190) is the most significant byte and SM91 (or SM191) is the
least significant byte.
SMB92
SMB93
SMB192
SMB193
Inter-character/message timer time-out value (in milliseconds). If the
time period is exceeded, the receive message is terminated.
SM92 (or SM192) is the most significant byte, and SM93 (or SM193)
is the least significant byte.
SMB94 SMB194 Maximum number of characters to be received (1 to 255 bytes).
Note: This range must be set to the expected maximum buffer size,
even if the character count message termination is not used.
SMB98 and SMB99
As described in Table C-17, SMB98 and SMB99 give you information about the
number of errors on the expansion I/O bus.
Table C-17 Special Memory Bytes SMB98 and SMB99
SM Byte
Description
SMB98
SMB99
This location is incremented each time a parity error is detected on the
expansion I/O bus. It is cleared upon power up, and by the user writing zero.
SMB98 is the most significant byte.