Filter
Top Products
Adapter Internal Registers
A-28
Table A–12. Network Configuration Register Bits (Continued)
Bit Name Function
12 RxCRC Receive CRC: When this bit is set to 1, the ThunderLAN controller transfers frame CRC
to the host for received frames and includes it in the reported frame length. The value
in the MaxRx register must be large enough to accommodate the data field plus this
transferred CRC. Failure to do so may result in an Rx overrun
11 PEF Pass error frames: When this bit is set to 1 and the CAF bit is set in NetCmd (copy all
frames mode), frames that would otherwise be rejected by the adapter due to CRC,
alignment, or coding errors are passed to the host. Such frames have the Rx_Error bit
in the list receive CSTAT set to differentiate them from good frames. This mode does not
affect adapter frame statistics.
10 One
fragment
One fragment mode: When this bit is set to 1, the adapter only reads a single fragment
(data count/data address pair) on the receive channel (rather than ten). When this bit
is set to 0, the adapter reads and uses up to ten fragments.
If multifragment mode is selected and less than ten fragments are used, the host must
write a 0 to the data count field of the fragment immediately after the last fragment used.
Generally, receive frames are not fragmented because they must be examined by host
software first. One fragment mode can be used in such cases, where it improves adapt-
er performance by reducing the number of PCI cycles needed to read the receive list.
9 One chn One channel mode: When this bit is set to 1, the adapter only supports a single transmit
channel (rather than two). When this bit is set to 0, the adapter supports two transmit
channels.
The adapter has 3K bytes of FIFO RAM for frame buffering. In normal two-channel
mode, 1.5K is allocated to Rx (one Rx channel), and 1.5K to transmit (0.75K per Tx
channel). In one-channel mode, all 1.5K of Tx FIFO RAM is allocated to channel 0, the
only channel. In one-channel mode, the HOST_CMD bit operations on channel 1 are
ignored.
8 MTEST Manufacturing test: When this bit is set to 1, the adapter is placed into manufacturing
test mode. Manufacturing test mode is reserved for Texas Instruments manufacturing
test. Operation of the adapter with this bit set is undefined.
7 PHY_En On-chip PHY enable: This bit is used to enable/disable the adapter’s on-chip 10Base-T
PHY. When this bit is set to 0, the on-chip PHY is disabled and placed in a powered-down
state. When this bit is set to a 1, the on-chip PHY is enabled as a potential PHY on the
shared MII (it still needs to be selected/configured using MDCLK/MDIO).
†
6–0 MAC select MAC protocol select: This field is used to select the network MAC protocol required. The
seven-bit code allows for 128 unique network configurations. This version of
ThunderLAN supports four protocol modes: CSMA/CD and three types of data stream
interfaces (supporting external demand priority and token ring implementations). Bits 6
through 2 are, therefore, hardwired to 0.
†
If the on-chip PHY is selected as the active MII PHY, all MII pins except MDCLK and MDIO are disabled.