182
Am79C976
8/01/00
P R E L I M I N A R Y
when it fetches a receive De-
scriptor. RDMD is cleared by
H_RESET or by S_RESET.
RDMD is unaffected by setting
the STOP bit.
12
CHDPOLL
Disable Chain Polling. If CHD-
POLL is set, the Buffer Manage-
ment Unit will disable chain
polling. Likewise, if CHDPOLL is
cleared, automatic chain polling
is enabled.
If CHDPOLL is set and
the Buffer Management Unit is in the
middle of a buffer-changing opera-
tion, setting the RDMD bit in CMD0 or
CSR7 will cause a poll of the current
receive descriptor, and setting the
TDMD bit in CMD0 or CRR0 will
cause a poll of the current transmit
descriptor.
If CHDPOLL is set, the
RDMD bit in CSR7 can be set to
initiate a manual poll of a receive
or transmit descriptor if the Buffer
Management Unit is in the middle
of a buffer-chaining operation.
Read/Write accessible. CHD-
POLL is cleared by H_RESET.
CHDPOLL is unaffected by
S_RESET or by setting the STOP
bit.
11
STINT
Software Timer Interrupt. The
Software Timer interrupt is set by
the Am79C976 controller when
the Software Timer counts down
to 0. The Software Timer will im-
mediately load the STVAL (BCR
31, bits 5-0) into the Software
Timer and begin counting down.
When STINT is set to 1, INTA is
asserted if the enable bit STINTE
is set to 1.
Read/Write accessible. STINT is
cleared by the host by writing a 1.
Writing a 0 has no effect. STINT
is cleared by H_RESET and is
not affected by S_RESET or set-
ting the STOP bit.
10
STINTE
Software Timer Interrupt Enable.
If STINTE is set, the STINT bit
will be able to set the INTR bit.
Read/Write accessible. STINTE
is set to 0 by H_RESET and is not
affected by S_RESET or setting
the STOP bit.
9
MREINT
MII Management Read Error In-
terrupt. The MII Read Error inter-
rupt is set by the Am79C976
controller to indicate that the cur-
rently read register from the ex-
ternal PHY is invalid. The
contents of BCR34 are incorrect
and that the operation should be
performed again. The indication
of an incorrect read comes from
the PHY. During the read turn-
around time of the MII manage-
ment frame the external PHY
should drive the MDIO pin to a
LOW state. If this does not hap-
pen, it indicates that the PHY and
the Am79C976 controller have
lost synchronization.
When MREINT is set to 1, INTA is
asserted if the enable bit MREIN-
TE is set to 1.
Read/Write accessible. MREINT
is cleared by the host by writing a
1. Writing a 0 has no effect. MRE-
INT is cleared by H_RESET and
is not affected by S_RESET or
setting the STOP bit.
8
MREINTE
MII Management Read Error In-
terrupt Enable. If MREINTE is
set, the MREINT bit will be able to
set the INTR bit.
Read/Write accessible. MREIN-
TE is set to 0 by H_RESET and is
not affected by S_RESET or set-
ting the STOP bit
7
MAPINT
MII Management Auto-Poll Inter-
rupt. This bit is set when the
Auto-Poll State Machine detects
a change in any PHY register that
is polled by the Auto-Poll State
Machine.
When MAPINT is set to 1, INTA is
asserted if the enable bit MAP-
INTE is set to 1.
Read/Write accessible. MAPINT
is cleared by the host by writing a
1. Writing a 0 has no effect. MAP-
INT is cleared by H_RESET and