HP 83620A, 24A, 22A manual Transition Filter, Event Register, Enable Register, An Example Sequence

There may or may not be a command to read a particular condition register.

Transition Filter

The transition filter specifies which types of bit state changes in the condition register will set corresponding bits in the event register. Transition filter bits may be set for positive transitions (PTR), negative transitions (NTR), or both. Positive means a condition

bit changes from 0 to 1. Negative means a condition bit changes from 1 to 0. Transition filters are read-write. Transition filters are unaffected by *CLS (clear status) or queries. They are set to instrument dependent values at power on and after *RST.

Event Register

The event register latches transition events from the condition register, as specified by the transition filter. Bits in the event register are latched, and once set they remain set until cleared by a query or a *CLS (clear status). There is no buffering, so while an event bit is set, subsequent events corresponding to that bit are ignored. Event registers are read-only.

Enable Register

The enable register specifies the bits in the event register that can generate a summary bit. The instrument logically ANDs corresponding bits in the event and enable registers, and ORs all the resulting bits to obtain a summary bit. Summary bits are in turn recorded in the Status Byte. Enable registers are read-write. Querying an enable register does not affect it. There is always a command to read and write to the enable register of a particular status group.

An Example Sequence

Figure l-34 illustrates the response of a single bit position in a typical status group for various settings. The changing state of the condition in question is shown at the bottom of the figure. A small binary table shows the state of the chosen bit in each status register at the selected times Tl to T5.

l-102 Getting Started Programming