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148
Am79C973/Am79C975
P R E L I M I N A R Y
CSR61: Previous Transmit Descriptor Address
Upper
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
PXDAU
Contains the upper 16 bits of the
previous transmit descriptor ad-
dress pointer. The Am79C973/
Am79C975 controller has the ca-
pability to stack multiple transmit
frames.
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.
CSR62: Previous Transmit Byte Count
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-12 RES
Reserved locations.
11-0
PXBC
Previous Transmit Byte Count.
This field is a copy of the BCNT
field of TMD1 of the previous
transmit 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.
CSR63: Previous Transmit Status
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
PXST
Previous Transmit Status. This
field is a copy of bits 31-16 of
TMD1 of the previous transmit
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.
CSR64: Next Transmit Buffer Address Lower
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NXBAL
Contains the lower 16 bits of the
next transmit buffer address from
which the Am79C973/Am79C975
controller will transmit an outgo-
ing frame.
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.
CSR65: Next Transmit Buffer Address Upper
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NXBAU
Contains the upper 16 bits of the
next transmit buffer address from
which the Am79C973/Am79C975
controller will transmit an outgo-
ing frame.
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.
CSR66: Next Transmit Byte Count
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-12 RES
Reserved locations. Read and
written as zeros.
11-0
NXBC
Next Transmit Byte Count. This
field is a copy of the BCNT field of
TMD1 of the next transmit 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.