GR740-UM-DS, Nov 2017, Version 1.7
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GR740
35.6.5 The transmission process
When the transmitter enable bit in the DMA channel control/status register is set the core starts read-
ing descriptors immediately. The number of bytes indicated are read and transmitted. When a trans-
mission has finished, status will be written to the first field of the descriptor and a packet sent bit is set
in the DMA control register. If an interrupt was requested it will also be generated. Then a new
descriptor is read and if enabled a new transmission starts, otherwise the transmit enable bit is cleared
and nothing will happen until it is enabled again.
15
Link error (LE) - A Link error occurred during the transmission of this packet.
14
Interrupt enable (IE) - If set, an interrupt will be generated when the packet has been transmitted and
the transmitter interrupt enable bit in the DMA control register is set.
13
Wrap (WR) - If set, the descriptor pointer will wrap and the next descriptor read will be the first one
in the table (at the base address). Otherwise the pointer is increased with 0x10 to use the descriptor at
the next higher memory location.
12
Enable (EN) - Enable transmitter descriptor. When all control fields (address, length, wrap and crc)
are set, this bit should be set. While the bit is set the descriptor should not be touched since this
might corrupt the transmission. The GRSPW clears this bit when the transmission has finished.
11: 8
Non-CRC bytes (NONCRCLEN)- Sets the number of bytes in the beginning of the header which
should not be included in the CRC calculation. This is necessary when using path addressing since
one or more bytes in the beginning of the packet might be discarded before the packet reaches its
destination.
7: 0
Header length (HEADERLEN) - Header Length in bytes. If set to zero, the header is skipped.
Table 547.
GRSPW transmit descriptor word 1 (address offset 0x4)
31
0
HEADERADDRESS
31: 0
Header address (HEADERADDRESS) - Address from where the packet header is fetched. Does not
need to be word aligned.
Table 548.
GRSPW transmit descriptor word 2 (address offset 0x8)
31
24 23
0
RESERVED
DATALEN
31: 24
RESERVED
23: 0
Data length (DATALEN) - Length in bytes of data part of packet. If set to zero, no data will be sent.
If both data- and header-lengths are set to zero no packet will be sent.
Table 549.
GRSPW transmit descriptor word 3(address offset 0xC)
31
0
DATAADDRESS
31: 0
Data address (DATAADDRESS) - Address from where data is read. Does not need to be word
aligned.
Table 546.
GRSPW transmit descriptor word 0 (address offset 0x0)