Am79C971
133
Read/Write accessible only when
either the STOP or the SPND bit
is set. LOOP is cleared by
H_RESET or S_RESET and is
unaffected by STOP.
1
DTX
Disable
Am79C971 controller not access-
ing the Transmit Descriptor Ring
and, therefore, no transmissions
are attempted. DTX = 0, will set
TXON bit (CSR0 bit 4) if STRT
(CSR0 bit 1) is asserted.
Transmit
results
in
Read/Write accessible only when
either the STOP or the SPND bit
is set.
0
DRX
Disable Receiver results in the
Am79C971 controller not access-
ing the Receive Descriptor Ring
and, therefore, all receive frame
data are ignored. DRX = 0, will
set RXON bit (CSR0 bit 5) if
STRT (CSR0 bit 1) is asserted.
Read/Write accessible only when
either the STOP or the SPND bit
is set.
CSR16: Initialization Block Address Lower
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
IADRL
This register is an alias of CSR1.
Read/Write accessible only when
either the STOP or the SPND bit
is set.
CSR17: Initialization Block Address Upper
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
IADRH
This register is an alias of CSR2.
Read/Write accessible only when
either the STOP or the SPND bit
is set.
CSR18: Current Receive Buffer Address Lower
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
CRBAL
Contains the lower 16 bits of the
current receive buffer address at
which the Am79C971 controller
will store incoming frame data.
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.
CSR19: Current Receive Buffer Address Upper
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
CRBAU
Contains the upper 16 bits of the
current receive buffer address at
which the Am79C971 controller
will store incoming frame data.
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.
CSR20: Current Transmit Buffer Address Lower
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
CXBAL
Contains the lower 16 bits of the
current transmit buffer address
from which the Am79C971 con-
troller is transmitting.
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.
CSR21: Current Transmit Buffer Address Upper
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.