Am79C971
137
CSR42: Current 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
CXBC
Current Transmit Byte Count.
This field is a copy of the BCNT
field of TMD1 of the current trans-
mit 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.
CSR43: Current Transmit Status
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
CXST
Current Transmit Status. This
field is a copy of bits 31-16 of
TMD1 of the current 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.
CSR44: Next Receive 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
NRBC
Next Receive Byte Count. This
field is a copy of the BCNT field of
RMD1 of the next 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.
CSR45: Next Receive Status
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
NRST
Next Receive Status. This field is
a copy of bits 31-16 of RMD1 of
the next receive 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.
CSR46: Transmit Poll Time Counter
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0
TXPOLL
Transmit Poll Time Counter. This
counter is incremented by the
Am79C971 controller microcode
and is used to trigger the transmit
descriptor ring polling operation
of the Am79C971 controller.
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.
CSR47: Transmit Polling Interval
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
15-0 TXPOLLINT
Transmit Polling Interval. This
register contains the time that the
Am79C971 controller will wait be-
tween successive polling opera-
tions. The TXPOLLINT value is
expressed as the two
’
s comple-
ment of the desired interval,
where each bit of TXPOLLINT
represents 1 clock period of time.
TXPOLLINT[3:0] are ignored.
(TXPOLLINT[16] is implied to be
a one, so TXPOLLINT[15] is sig-
nificant and does not represent
the sign of the two
’
s complement
TXPOLLINT value.)