
8-12
General Control and Status Registers
`efmp69030 Databook
Revision 1.3 11/24/99
For the AR and DAC sub-indexed register groups:
Note: Write access to the indices for these two sub-indexed register groups must
be enabled using these 2 bits of this register, since these indices are controlled in
the same way as the actual sub-indexed registers of these groups.
Bit
1 0
Effect on Write Accesses to AR and
DAC Sub-indexed Register Groups
0 0
All write access from the I/O space to these sub-indexed
register groups of both pipelines is disabled.
0 1
The AR and DAC sub-indexed register groups that belong
to pipeline A are made writable from the I/O space using
pipeline A’s indices for these register groups. Neither the
AR or DAC sub-indexed register groups that belong to
pipeline B, or their indices, are writable from the I/O space.
If bit 1 of pipeline A’s shadow of XR09 is set to 0, then the
index register for pipeline A’s AR register group (ARX) tog-
gles between being an index and a data port when written
to, and reading from pipeline A’s shadow of ST01 sets
ARX to being an index.
If bit 1 of pipeline A’s shadow of XR09 is set to 1, then the
index register for pipeline A’s AR register group (ARX) re-
mains locked as being only an index register.
1 0
The AR and DAC sub-indexed register groups that belong
to pipeline B are made writable from the I/O space using
pipeline B’s indices for these register groups. Neither the
AR or DAC sub-indexed register groups that belong to
pipeline A, or their indices, are writable from the I/O space.
If bit 1 of pipeline B’s shadow of XR09 is set to 0, then the
index register for pipeline A’s AR register group (ARX) tog-
gles between being an index and a data port when written
to, and reading from pipeline B’s shadow of ST01 sets
ARX to being an index.
If bit 1 of pipeline A’s shadow of XR09 is set to 1, then the
index register for pipeline A’s AR register group (ARX) re-
mains locked as being only an index register.
1 1
Write access from the I/O space to the AR and DAC sub-
indexed register groups of both pipelines is enabled.
For whichever pipeline wherein bit 1 of XR09 is set to 0,
the index register for that pipeline’s AR register group
(ARX) toggles between being an index and a data port
when written to, and reading from EITHER pipeline’s shad-
ow of ST01 will set it to being an index.
For whichever pipeline wherein bit 0 of XR09 is set to 1,
the index register for that pipeline’s AR register group
(ARX) remains locked as being only an index register.