Siemens 6ES7321-1CH80-0AA0 Digital Input Module — Legacy Replacement. Siemens 6ES7321-1CH80-0AA0 is the exact manufacturer order number for a digital input module in the SIMATIC S7-300 portfolio. Siemens describes this exact reference as: SIMATIC S7-300, DIGITAL INPUT SM 321, OPTICALLY ISOLATED, FOR EXPANDED TEMPERATURE RANGE, 16 DI, DC 48 - 125V, 20 PIN. The verified manufacturer lifecycle record is PM500:Discontinued Product or end of PLM & Support.