116
Am79C973/Am79C975
P R E L I M I N A R Y
RMABORT
Am79C973/Am79C975 controller
and cleared by writing a 1. Writ-
ing a 0 has no effect. RMABORT
is cleared by H_RESET and is
not affected by S_RESET or by
setting the STOP bit.
is
set
by
the
12
RTABORT
Received Target Abort. RT-
ABORT is set when a target ter-
minates
an
Am79C975 master cycle with a
target abort sequence.
Am79C973/
RTABORT
Am79C973/Am79C975 controller
and cleared by writing a 1. Writ-
ing a 0 has no effect. RTABORT
is cleared by H_RESET and is
not affected by S_RESET or by
setting the STOP bit.
is
set
by
the
11
STABORT
Send Target Abort. Read as ze-
ro; write operations have no ef-
fect. The Am79C973/Am79C975
controller will never terminate a
slave access with a target abort
sequence.
STABORT is read only.
10-9
DEVSEL
Device Select Timing. DEVSEL
is set to 01b (medium), which
means that the Am79C973/
Am79C975 controller will assert
DEVSEL two clock periods after
FRAME is asserted.
DEVSEL is read only.
8
DATAPERR
Data Parity Error Detected.
DATAPERR is set when the
Am79C973/Am79C975 controller
is the current bus master and it
detects a data parity error and the
Parity Error Response enable bit
(PCI Command register, bit 6) is
set.
During the data phase of all
memory read commands, the
Am79C973/Am79C975 controller
checks for parity error by sam-
pling the AD[31:0] and C/BE[3:0]
and the PAR lines. During the
data phase of all memory write
commands,
the
Am79C975 controller checks the
Am79C973/
PERR input to detect whether the
target has reported a parity error.
DATAPERR
Am79C973/Am79C975 controller
and cleared by writing a 1. Writ-
ing a 0 has no effect. DATAPERR
is cleared by H_RESET and is
not affected by S_RESET or by
setting the STOP bit.
is
set
by
the
7
FBTBC
Fast
Read as one; write operations
have no effect. The Am79C973/
Am79C975 controller is capable
of accepting fast back-to-back
transactions with the first transac-
tion addressing a different target.
Back-To-Back
Capable.
6-5
RES
Reserved locations. Read as
zero; write operations have no ef-
fect.
4
NEW_CAP New Capabilities. This bit indi-
cates whether this function imple-
ments
a
capabilities such as PCI power
management. When set, this bit
indicates the presence of New
Capabilities. A value of 0 means
that this function does not imple-
ment New Capabilities.
list
of
extended
Read as one; write operations
have no effect. The Am79C973/
Am79C975 controller supports
the Linked Additional Capabilities
List.
3-0
RES
Reserved locations. Read as
zero; write operations have no ef-
fect.
PCI Revision ID Register
Offset 08h
The PCI Revision ID register is an 8-bit register that
specifies the Am79C973/Am79C975 controller revision
number. The value of this register is 4Xh with the lower
four bits being silicon-revision dependent.
The PCI Revision ID register is located at offset 08h in
the PCI Configuration Space. It is read only.
PCI Programming Interface Register
Offset 09h
The PCI Programming Interface register is an 8-bit reg-
ister that identifies the programming interface of
Am79C973/Am79C975 controller. PCI does not define