A simulation technique to test on board software — EEPROM hardware interface using SILS facility

摘要

ISRO Satellite Centre (ISAC) is the lead centre for development and operationalisation of communication, remote sensing and interplanetary missions. These satellites contain highly advanced embedded systems carrying out critical operations thus achieving mission goals. In the ISRO's current generation of spacecrafts, as autonomy taking the centre stage, complexity of spacecrafts have increased manifold. Attitude and Orbit Control Electronics (AOCE), is one of the main subsystems where most of the autonomy features are implemented. To handle autonomy functionalities, Electrically Erasable and Programmable Read Only Memory Management (EEPROM) is interfaced with AOCE On board software. On-board autonomy functions use data and logics stored in EEPROM memory via onboard software. Testing these interface logics had an inherent constraint in performing number of write operations on EEPROM device[1]. Overcoming this limitation and performing exhaustive testing of autonomy and EEPROM interface logics was a challenge. Simulation based test facility was already established to test all on-board software functionalities. Hence, EEPROM memory device had to be simulated and interfaced with this test facility, in order to test on-board autonomy functions. In addition, along with EEPROM, other memory devices like, Storage Random Access Memory (RAM) and Programmable Read Only Memory (PROM) are used for various critical functionalities. Having a device specific simulation model for EEPROM, Storage RAM and Programmable Read Only Memory (PROM) although technically feasible, lacks software reusability, thereby increasing development and testing time. To make the memory controller simulation more generic and reusable object oriented methodology was used [2]. The design model described in the rest of the paper provides an overview of the same. This paper focuses, mainly on the design methodology used to simulate EEPROM as a case study. This paper also discusses in brief the results obtained by testing using this simulation technique and advantages reaped from the same.