Technical information

7-73
Register Descriptions
MacConfig2 Register
Type: R/W
Internal Registers Subgroup: MAC Registers
Byte Address: 5004h- 5007h
Table 7-92. MacConfig2 Register
Bit(s) rw
Reset
Value Description/Function
31:16 r/w 0
Reserved:
Always read as 0.
15 r 0
TxCRCerr:
Transmit Ethernet CRC error status.
14 r 0
TxIslCRCerr:
Transmit ISL (Interswitch Link) CRC error status.
13 r 0
RxCRCerr:
Receive Ethernet CRC error status.
12 r 0
RxIslCRCerr:
Receive ISL CRC error status.
11 r 0
TXCF:
Transmit Control Frame.
10 r/w 0
CtlSoftRst:
Flow control module soft reset. This bit has no effect on
any configuration register state.
9r/w0
RxSoftRst:
Receive module soft reset. This bit has no effect on any
configuration register state.
8r/w0
TxSoftRst:
Transmit module soft reset. This bit has no effect on any
configuration register state.
7r/w0
RxISLEn:
This bit enables the Rx ISL function. When this bit is
cleared, regular Ethernet frames are received. The Address Filtering
block qualifies this bit with the first 40-bits of the ISL frame header.
6r/w0
BackPressureNoBackOff:
When this bit is reset, the Transmit Half
Duplex Flow Control bit in the configuration register is ignored.
When this bit is set, the transmit engine optionally asserts back
pressure with or without the back off delay algorithm dependent on
Transmit Half Duplex Flow Control bit.
5r/w0
AutoVlanPad:
This bit may be set only when
P
AD
E
N
is also set in
the
M
AC
C
ONFIG
1
register. When
A
UTO
V
LAN
P
AD
and
P
AD
E
N
are
set, the padding is to 60 for a non-VLAN frame and to 64 for VLAN
type frames. A VLAN frame is detected when the VLAN type
matches the value contained in the VLAN Type register.
Note:
If the AIC-6915 is required to calculate and add the CRC, then
the minimum frame size is 64 for non-VLAN frames, and 68 for a
VLAN type frames.
4r/w0
MandatoryVLANPad:
Mandatory VLAN pad. When this bit is set,
padding out to 64-bytes always occurs.
3r/w0
TxISLAppen/TxISLCrcEn:
Enables ISL hardware CRC generation
function. When the bit is reset, the hardware does not append the 4-
byte CRC at the end of the frame. Instead, it checks the correctness
of the user supplied CRC bytes and flags error accordingly. When
this bit is set, hardware a appends 4-byte ISL CRC in addition to
normal Ethernet CRC bytes. This bit does not affect the receive
operation.