Interrupt Identification Register; Table 5-2. Interrupt Types And Priorities - National Instruments GPIB-COM User Manual

Section Five

Interrupt Identification Register

Offset from Base I/O Address = 2
Register Address = XFA
7 6
0
0
The Interrupt Identification Register is a read-only register which tells you when an interrupt is
pending and if so, what kind of interrupt it is. This register functions identically on the GPIB-
COM and the INS8250.
Bit Mnemonic
7-3r 0
2-1r ID[1-0]
0r INT
© National Instruments Corporation
5 4
0 0
Description
Reserved Bits 7 through 3
These bits always read as 0.
Identify Interrupt Register Bits
These two bits identify the interrupt that is pending. If more
than one interrupt is pending, only the one with the highest
priority is identified. The types and priorities are given in Table
5-2.

Table 5-2. Interrupt Types and Priorities

Bit 2 Bit 1
0 0
0 1
1 0
1 1
Interrupt Pending Bit
This bit is clear if an interrupt is pending. If set, no interrupt is
pending.
5-7
Programming the GPIB-COM
3 2
ID1 ID0
0
Type of Interrupt
Receiver Line Status
Received Data Available
Transmitter Holding
Register Empty
Modem Status
1
0 R
INT
Priority
1st
2nd
3rd
4th
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