Smb2: Freeport Receive Character; Smb3: Freeport Character Error - Siemens SIMATIC S7 System Manual

Special memory (SM) and system symbol names
D.4 SMB2: Freeport receive character
D.4

SMB2: Freeport receive character

Special memory byte 2 is the Freeport receive character buffer. While in Freeport mode, the
CPU stores each character that the CPU receives in this byte for easy access by your
program.
Table D- 3 SMB2 Freeport received character
S7-200 SMART SM address
symbol name
Receive_Char SMB2
Note
Port 0 and Port 1 share SMB2 and SMB3
When the CPU receives a character on Port 0, note the following:
• The CPU executes the interrupt routine attached to that event (interrupt event 8).
• SMB2 contains the character received on Port 0.
• SMB3 contains the parity status of the received character.
Likewise, when the CPU receives a character on Port 1, note the following:
• The CPU executes the interrupt routine attached to that event (interrupt event 25).
• SMB2 contains the character received on Port 1.
• SMB3 contains the parity status of the received character.
D.5

SMB3: Freeport character error

The CPU sets SM3.0 TRUE when Freeport communication detects a parity, framing, break,
or overrun error on a received character. Use this bit to discard the message.
Table D- 4 SMB3 Freeport character error
S7-200 SMART SM address
symbol name
Parity_Err SM3.0
804
Description
This byte contains each character that the CPU receives from Port 0 or Port 1 during
Freeport communication.
Description
This bit indicates that the CPU received a parity, framing, break, or overrun error
from Port 0 or Port 1:
FALSE: no error
•
TRUE: error
•
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART