Question: What is the primary purpose of using a NULL procedure byte ('60') in the SIM-ME interface, and what alternative approach is recommended for SIM Application Toolkit activities that require more processing time?
Option 1: To immediately terminate a command-response pair, with no alternative for extending processing time.
Option 2: To allow the ME to send multiple commands simultaneously, with NULL procedure bytes being the only means to manage timing.
Option 3: To provide the SIM with more time to respond to a command, but for SIM Application Toolkit activities, using a MORE TIME command is recommended instead.
Option 4: To notify the ME of a SIM error, requiring an immediate restart of the command sequence.
Explanation: The NULL procedure byte ('60') is used to give the SIM more time to respond to a command, effectively pausing the command-response sequence. However, in the context of SIM Application Toolkit activities that are time-consuming, utilizing a MORE TIME command (as defined in TS 11.14 for SAT) is preferred. This approach not only grants the SIM additional processing time but also frees up the SIM/ME interface, preventing potential bottlenecks for time-critical commands like RUN GSM ALGORITHM.