• Expansion limits
  • Length of cable: Max. 20 m
  • Max. 32 bytes of input and output data per port
  • Max. 32 bytes of input and output data per module

LED indicators

• DIAG: Operating state indicator (green/red) of the module
• C1..C4: Port status indicator (green) for Port 1, 2, 3 and 4
• Q1..Q4: Channel status indicator (green) for Port 1, 2, 3 and 4
• F1..F4: Port fault indicator (red) for Port 1, 2, 3 and 4

Depending on the CPU type used, as many as 8 SM 1278 modules can be used on one S7-1200 CPU.