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GO Command
6-8
Depending on the value loaded into the Ld_Thr bit in the HOST_CMD register,
ThunderLAN gives a Tx EOF interrupt after processing the number of frames
specified. In this case, the driver acknowledges the number of frames that it
has processed. Again, the driver has to look into the Frm_Cmp bit of the
CSTAT field to determine the number of frames that have been processed.
The transmit open channel command (Tx GO) initializes frame transmission
into ThunderLAN’s internal transmit FIFO and subsequently to the network.
There are two steps involved in issuing a Tx GO command:
1) In the CH_PARM register, write the physical address of the beginning of
the list structure. ThunderLAN uses this physical address to DMA data
from host memory.
2) In the HOST_CMD register, write the appropriate bits to start the channel.
The Tx GO command writes to the GO bit, and selects the transmit chan-
nel by writing to Ch_Sel. R/T must be set to 0, indicating a transmit com-
mand.
The HOST_CMD register can be written in a single, 32-bit operation. This im-
plies that several commands can be combined in one operation. Ack and Tx
GO commands can be issued in a single operation.