SMSC LAN1198 Manual De Usuario

LAN9118 Family Programmer Reference Guide

SMSC AN 12.12

35

Revision 1.0 (12-14-09)

 

Once the device is initialized, the application can continue sending packets until the first indication
appears that the device can no longer accept packets (since we cannot know the size of the next
transmit packet a priori, we want to ensure that we can send the largest packet possible, 1518 bytes
in size).  At that point we tell the network operating system (NOS) to stop sending the driver any more
transmit packets.  When the device has freed up enough buffer space, due to the transmitting of
packets internally queued, it interrupts the application, which disables the interrupt and calls into the
NOS telling it that we can now resume accepting packets for transmit.

For simplicity and completeness, this example shows the TX status results processing handled as a
thread scheduled directly at the entry of the packet transmit function.  In truth this thread of execution
could be scheduled from its own TX Status FIFO Level Interrupt (TSFL),  which signals that a
threshold number of packets have completed the transmit process (successful or not).

Can the FIFO accept the

next packet?

(TX_FIFO_INF:TDFREE )

Block NOS queuing

mechanism which

otherwise calls Hard

Transmit Packet

Set FIFO_INT:TX

to largest possible

sized packet (0x18),

Enable TDFA_INT_EN

interrupt

return OK;

Hard Transmit

Packet

Interrupt Service Routine

Disable TDFA_INT_EN interrupt on

exceeding marker

Un-block NOS queuing mechanism

which would call Hard Transmit Packet

ISR Complete

TDFA Interrupt: TDFREE threshold

reached

Transfer TX Cmd Words, Data Memory Buffer

to TX Data FIFO

Free up NOS Data Memory Buffer

Accumulated TX stats

to process?

Schedule NOS thread to evaluate  TX Status

for each packet sent, accumulate common

driver statistics and clear TX Status  FIFO