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PEB 20321
PEF 20321
Host Memory Organization
Data Sheet
298
2001-02-14
is sent.
During transmit abort the TF does not access the Tx buffer. The handling of the link
list is not affected by the transmit abort, i.e. the device keeps the TB full. When the
transmit abort is withdrawn, the Tx formatter continues the transmission with the data
stored in TB. In the case of HDLC or TMB or TMR mode the remaining data of the
aborted HDLC or TMB frame is sent as a new independent frame. To avoid this
problem the link list must be reinitialized by a transmit initialization command together
with the revoking of the transmission abort.
Another proper use of the transmit abort command consists in setting the last
descriptor of the last frame to be transmitted with HOLD =
‘
1
’
and waiting for the
device to poll the HOLD bit (ITBS + 2) times where ITBS is the number of DWORDs
assigned to this channel currently. Afterwards TB is empty and the transmit abort then
issued does not abort a currently sent frame. The same procedure can also be used
for the transmit off command.
–
Transmit Jump
TI =
‘
1
’
, TO =
‘
0
’
, TA =
‘
0
’
(clears a transmit off and transmit abort condition, affects
only the DMA interface)
This bit is set only during normal operation. Then the MUNICH32X branches to the
transmit descriptor (FTDA) specified in the CCB after finishing the current
Tx descriptor without interrupting or aborting the transmitted frame.
The DMA controller will proceed finishing the current transmit descriptor as usual and
afterwards branch to the new descriptor specified by FTDA. If the current descriptor
does not include a frame end (FE = 0) (HDLC, TMB, TMR) the DMA controller will link
the following data section(s) of the
‘
new
’
descriptor chain to the opened frame. This
may generate unexpected frames.
–
Transmit Initialization
TI =
‘
1
’
, TO =
‘
0
’
, TA =
‘
1
’
(clears a previous transmit abort condition, affects the DMA
interface and the serial interface)
Before the MUNICH32X has received a transmit initialization command, it will not
transmit correctly on the channel. This command should therefore be the first channel
command after a pulse at the reset pin for a channel.
FTDA is then the address of the starting point of the Tx descriptor for chaining list. In
this case the transmit initialize command should be accompanied by the NITBS bit set
and a reasonable value for ITBS (0 < ITBS < 64).
If the command is issued during normal operation it only affects the DMA. The
MUNICH32X stops processing of the current link list and branches to the Tx descriptor
at the FTDA address. The data stored in the TB are discarded and the TB is filled with
the data of the new descriptor.