136
Am79C971
15-0
CXDAU
Contains the upper 16 bits of the
current transmit descriptor ad-
dress pointer.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR36: Next Next Receive Descriptor Address
Lower
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NNRDAL
Contains the lower 16 bits of the
next next receive descriptor ad-
dress pointer.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR37: Next Next Receive Descriptor Address
Upper
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NNRDAU
Contains the upper 16 bits of the
next next receive descriptor ad-
dress pointer.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR38: Next Next Transmit Descriptor Address
Lower
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NNXDAL
Contains the lower 16 bits of the
next next transmit descriptor ad-
dress pointer.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR39: Next Next Transmit Descriptor Address
Upper
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NNXDAU
Contains the upper 16 bits of the
next next transmit descriptor ad-
dress pointer.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR40: Current Receive Byte Count
Bit
31-16
Name
RES
Description
Reserved locations. Written as
zeros and read as undefined.
15-12
RES
Reserved locations. Read and
written as zeros.
11-0
CRBC
Current Receive Byte Count.
This field is a copy of the BCNT
field of RMD1 of the current re-
ceive descriptor.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.
CSR41: Current Receive Status
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
CRST
Current Receive Status. This
field is a copy of bits 31-16 of
RMD1 of the current receive de-
scriptor.
Read/Write accessible only when
either the STOP or the SPND bit
is set. These bits are unaffected
by H_RESET, S_RESET, or
STOP.