The S7-200 system supports 242 I/O and a maximum expansion modules supported are 8 including CPU. The CPUs available in S7-200 system are inbuilt with certain number of I/Os. Many CPUs are available such as 222,224, 224 XP and 226. Excellent choice for small and medium applications . Various special communication modules are available for making system suitable for Profibus, Ethernet etc. S7-200 CN systems are economical range of PLC modules with CE certification.
Refer www.support.automation.siemens.com for complete range of products.