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78 HP E1459A Register Definitions
Manufacturer ID
Register
ID register (base = 00
h
) is a read only register. For the Isolated Digital
Input/Interrupt, a read of the ID register returns FFFF
h
since the
multiplexers are manufactured by Hewlett-Packard and are A16 only,
register-based devices.
Manufacturer ID Register (base + 00
h
)
* Returns FFFF
h
= Hewlett-Packard A16 (only) register-based device
Device Type
Register
Device Type register (base = 02
h
) is a read only register. For the Isolated
Digital Input/Interrupt, a read of the Device Type register returns 0154
h
.
This indicates it is a model HP E1459A.
Device Type Register (base + 02
h
)
Status/Control
Register
Status/Control register (base = 04
h
) can be read and written. Many of the
bits perform control functions. Reading this register returns the current state
of the status bits for the module.
Status/Control Register (base + 04
h
)
NOTE: Bits 8 and 9 are returned in the IACK response in the same bit
positions.
WRITE
R = Reset to power-on state by writing a "1" in this bit (Must be set back to
"0").
BS = Bank Select. When "0" Port 0 and Port 1 data are accessed in registers
b + 10
h
through b + 2E
h
. When "1" Port 2 and Port 3 data are accessed in the
same registers.
I = Interrupt Enable. When set to 1, an IRQ can be generated with an edge
event (assuming one is enabled).
D = Data Ready Enable. When set to 1 an IRQ can be generated with a
DAVX line is asserted.
b + 0
h
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Write No Effect
Read Manufacturer ID
b + 2
h
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Write No Effect
Read Always Returns 0154
h
b + 4
h
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Write Undefined D I BS Undefined R
Read Undefined M Undefined D IRQ E IRQ Undefined D I BS Undefined R