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Sundance Technology ST201 PRELIMINARY draft 2
8. Verify EepromBusy is false.
9. Issue WriteRegister command
(opcode = 01 aaaa aaaa)
Step 4 through 8 may be skipped for certain types
of EEPROM devices.
ADAPTER TXDMA SEQUENCE
Beginning with the host system writing to the TxD-
MAListPtr register (when starting from an empty
TxDMAList, for instance), the ST201 performs the
following procedure during transfers of TxDMA
frames.
1. Verifies the TxDMAListPtr is non-zero.
2. Verifies not in the TxDMAHalt state.
3. Fetches the second dword from the TFD
pointed to by TxDMAListPtr and writes this
value into the TxFIFO.
4. One by one, fetches the TxDMAFragAddr/TxD-
MAFragLen entries from the TFD, and moves
the associated data fragments to the TxFIFO.
5. Sets the TxDMAComplete bit in the TFD.
6. If TxDMAHalt is in effect, waits until a TxD-
MAResume is issued.
7. If a transmit under run has occurred, waits until
the host system sets the TxReset bit.
8. Re-fetches the TFC and, if the TxDMAIndicate
bit is set, sets TxDMAComplete (which may in
turn cause an interrupt if the IntEnable masks
are set appropriately)
9. Fetches the TxDMANextPtr from the current
TFD. If TxDMANextPtr is zero, the TxDMA
Logic becomes idle. If polling is disabled (TxD-
MAPollPeriod is zero), the TxDMA Logic waits
for a non-zero value to be written to TxDMAL-
istPtr. If polling is enabled (TxDMAPollPeriod
is non-zero), the old value in TxDMAListPtr is
preserved, and the ST201 polls on TxDMAN-
extPtr in the TFD until it fetches a non-zero
value from it. If the value fetched from TxD-
MANextPtr is non-zero, then the value is
loaded into TxDMAListPtr, advancing the
ST201 to the new TFD.
10. With a new TFD to process, the ST201 returns
to step 2.
ADDING TFD’S TO THE END OF THE
TXDMALIST
The following sequence describes the process for
adding TFD’s to the end of the TxDMAList when
TxDMA polling is disabled (TxDMAPollPeriod is
zero).
1. Set the TxDMAHalt bit.
2. Wait for the TxDMAHalt to complete by polling
on TxDMAHalted bit.
3. Update TxDMANextPtr in the last TFD in the
TxDMAList with the address of the TFD being
added.
4. Read TxDMAListPtr.
5. If TxDMAListPtr is zero, write the address of
the new TFD to TxDMAListPtr.
6. Resume the TxDMA Logic by setting TxD-
MAResume bit. The TxDMA Logic will become
idle when it fetches a zero TxDMANextPtr
value from a TFD. One way to restart the
TxDMA process is by writing a non-zero value
to TxDMAListPtr.
When polling is enabled (TxDMAPollPeriod is non-
zero), TFD’s can be added to the end of the TxD-
MAList with no register accesses by writing the
address of the new TFD in the last TFD’s TxD-
MANextPtr field.
INSERTING A TFD AT THE HEAD OF THE
TXDMALIST
TFD’s cannot be added before the active TFD in
the TxDMAList, they can only be added after the
active (unfinished) TFD. The following sequence
describes the process for adding TFD’s to the head
of the TxDMAList when TxDMA polling is disabled
(TxDMAPollPeriod is zero).
1. Set TxDMAHalt bit.
2. Wait for the TxDMAHalt to complete by polling
the TxDMAHalted bit. When halted, the TxD-
MAListPtr register will hold the address of the
TFD which just completed transfer into the
ST201 (the “last TFD in the TxDMAList”).
3. Find the last TFD in the TxDMAList, corre-
sponding to the TFD at the address held in the
TxDMAListPtr register. This will also be the last
TFD in the TxDMAList with the TxDMACom-
plete bit set.
4. Copy the value in the “last TFD’s” TxDMANex-
tPtr into the TxDMANextPtr field of the TFD to
be inserted.
5. Update TxDMANextPtr field in the “last TFD”
with the address of the inserted TFD.
6. Read TxDMAListPtr.
7. If TxDMAListPtr is zero, write the address of
the inserted TFD to TxDMAListPtr.
8. Resume the TxDMA Logic by setting TxD-
MAResume.
When polling is enabled (TxDMAPollPeriod is non-
zero), TFD’s can be inserted to the head of the
TxDMAList with no register accesses as follows.
1. Find the first TFD in the list with TxDMACom-
plete bit cleared (the “first TFD”).
2. Set the “first TFD’s” TxDMANextPtr to zero.
3. Check the TxDMAComplete bit of “the first
TFD”. If clear, proceed to the next step. If set,
it’s too late to insert the new TFD at the loca-