Comments 1. Setting the Transition Filter. When the digitizer is INITiated, a low-to-high transition of bit 6 in the condition register occurs indicating the digitizer is in the wait-for-arm state. When an arm is received, a high-to-low transition of bit 6 occurs. The power-on/reset setting of the transition filter allows the positive transition to be recognized and the negative transition to be ignored. Because the application is interested in the high-to-low transition, the transition filter is set for a negative transition of bit 6 (STATus:OPERation:NTRansition 64), and to ignore the positive transition (STATus:OPERation:PTRansition 0).

2.Setting the Enable Register. When the high-to-low transition occurs, the "event" is recorded by setting (to ’1’) a corresponding bit in the event register. (Event register bits are set from low-to-high regardless of the transition recognized by the transition filter.)

In order for the controller/computer to know that the event has occurred, the enable register is set such that the arm event sets a bit in the status byte (STATus:OPERation:ENABle 64).

3.Reading the Status Byte. Once the program initiates the digitizer (INIT command), the program continually monitors the digitizer status byte using *STB?. When the arm event occurs, bit 7 in the status byte is set. (Status byte bits are also set from low-to-high regardless of the transition recognized by the transition filter.) This signals the controller/computer that the event occurred. At this point, the program exits the loop and then prompts the user to press ’Enter’ which then triggers the digitizer (TRIGger:IMMediate).

Additional information on the digitizer status groups and on using the registers in the groups can be found in Chapter 3 - "Understanding the Digitizer".

102 Using the Digitizer

Chapter 2

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HP E1429A manual Using the Digitizer Chapter