DP83907VF National Semiconductor, DP83907VF Datasheet - Page 44

• Manufacturer Part Number: DP83907VF
• Description: IC CONTROLLR AT/LANII TP 160PQFP
• Manufacturer: National Semiconductor

Specifications of DP83907VF

• Controller Type: Network Interface Controller (NIC)
• Interface: Twisted Pair
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 150mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83907VF

6 0 Operation of DP83907
10) Take the DP83907 out of loopback This is done by
11) If the ‘‘Resend’’ variable is set to a 1 reset the ‘‘Re-
Note 1 If Remote DMA is not being used the DP83907 does not need to
Note 2 When the DP83907 is in ST0P mode the Missed Packet Tally
4) Clear the DP83907’s Remote Byte Count registers
5) Read the stored value of the TXP bit from step 1
6) Place the DP83907 in either mode 1 or mode 2 loop-
7) Issue the START command to the DP83907 This can
8) Remove one or more packets from the receive buffer
9) Reset the overwrite warning (OVW overflow) bit in the
(RBCR0 and RBCR1)
above
If this value is a 0 set the ‘‘Resend’’ variable to a 0 and
jump to step 6
If this value is a 1 read the DP83907’s Interrupt Status
Register If either the Packet Transmitted bit (PTX) or
Transmit Error bit (TXE) is set to a 1 set the ‘‘Resend’’
variable to a 0 and jump to step 6 If neither of these
bits is set place a 1 in the ‘‘Resend’’ variable and jump
to step 6
This step determines if there was a transmission in
progress when the stop command was issued in step 2
If there was a transmission in progress the DP83907’s
ISR is read to determine whether or not the packet was
recognized by the DP83907 If neither the PTX nor TXE
bit was set then the packet will essentially be lost and
retransmitted only after a time-out takes place in the
upper level software By determining that the packet
was lost at the driver level a transmit command can be
reissued to the DP83907 once the overflow routine is
completed (as in step 11) Also it is possible for the
DP83907 to defer indefinitely when it is stopped on a
busy network Step 5 also alleviates this problem Step
5 is essential and should not be omitted from the over-
flow routine in order for the DP83907 to operate cor-
rectly
back This can be accomplished by setting bits D2 and
D1 of the Transmit Configuration Register to ‘‘0 1’’ or
‘‘1 0’’ respectively
be accomplished by writing 22H to the Command Reg-
ister This is necessary to activate the DP83907’s Re-
mote DMA channel
ring
Interrupt Status Register
writing the Transmit Configuration Register with the val-
ue it contains during normal operation (Bits D2 and D1
should both be programmed to 0 )
send’’ variable and reissue the transmit command This
is done by writing a value of 26H to the Command Reg-
ister If the ‘‘Resend’’ variable is 0 nothing needs to be
done
be started before packets can be removed from the receive buffer
ring Hence step 8 could be done before step 7 eliminating or
reducing the time spent polling in step 5
counter is disabled
(Continued)
44
FIGURE 32 Overflow Routine
TL F 12082 – 27