Lexicon MPX-1 - Interrupt Control Commands

interrupt will be unmasked. Bit 0 of the mask byte corresponds to VIa. on the
bus, and Bit 7 corresponds to VI7* on the bus. This is the same as sending OCWl
to the interrupt controller (see the 8259A application note in the appendix of
this document for more information).
SENDEOI - SEND END-oF-INTERRUPT COMMAND TO INTERRUPT CONTROLLER
OPCODE BIT CODING:
Bit 7
Bit· 0
---------------------------------------------------------------
CONT lINT
o
o
o
o
1
1
PARAMETERS PASSED: EOI Command Byte, Link Address.
PARAMETERS RETURNED: None.
DESCRIPTION: This command is used to send an End-of-Interrupt Command to the
8259A interrupt controller. It is also useful for rotating the interrupt prior-
ity levels. The byte to be sent to the 8259A Is passed in Parameter Byte O.
This is equivalent to sending OCW2 to the 8259~ For more information on what
this byte does to the 8259A, refer to the 8259A application note contained in
the appendix of this document.
READREG - READ INTERRUPT CONTROLLER REGISTERS
OPCODE BIT CODING:
Bit 7
CONT I INT
o
o
1
o
Bit 0
o
PARAMETERS PASSED: Link Address.
PARAMETERS RETURNED: Contents of IS and IR registers in 8259A.
DESCRIPTION: This command is used to read the contents of the Interrupt Request
(IR) and In Service (IS) registers in the 8259~ It returns the contents of the
lR register in the Result 1 Byte location and the contents of the IS register in
the Result 2 Byte location. For more information on the meaning of the IS and
lR registers, see the 8259A application note in the appendix of this document.
SETRESPOBSE - SET INTERRUPT RESPONSE BYTE
OPCODE BIT CODING:
Bit 7
CONT I INT. I
o o
o
1
o
Bit 0
1
PARAMETERS PASSED: Response Byte, Link Address.
PARAMETERS RETURNED: None.
DESCRIPTION: The MPX-l is capable of putting an 8 bit value on the systam data
16