Each CPU requires a Micro Memory Card (MMC). Programming may be carried out using the Step 7 Lite software (stock no. ; 539-1755 539-1755 ). S7-312C. SIMATIC S7-300 - CPU312C - For small applications with high requirements in terms of processing power. Expandable using up to 1 rack (with 8 modules per rack) Dimensions: H125 x W40 x D130mm