GR712RC-UM, Jun 2017, Version 2.9 113 www.cobham.com/gaisler
GR712RC
header pointer and the data CRC is generated from data fetched from the data pointer. The CRCs are
appended after the corresponding fields. The NON-CRC bytes field is set to the number of bytes in
the beginning of the header field that should not be included in the CRC calculation.
The CRCs are sent even if the corresponding length is zero, but when both lengths are zero no packet
is sent not even an EOP.
16.5.4 Starting transmissions
When the descriptors have been initialized, the transmit enable bit in the DMA control register has to
be set to tell the GRSPW to start transmitting. New descriptors can be activated in the table on the fly
(while transmission is active). Each time a set of descriptors is added the transmit enable register bit
should be set. This has to be done because each time the GRSPW encounters a disabled descriptor this
register bit is set to 0.
Table 86. GRSPW transmit descriptor word 0 (address offset 0x0)
31 18 17 16 15 14 13 12 11 8 7 0
RESERVED DC HC LE IE WR EN NONCRCLEN HEADERLEN
31: 18 RESERVED
17 Append data CRC (DC) - Append CRC calculated according to the RMAP specification after the
data sent from the data pointer. The CRC covers all the bytes from this pointer. A null CRC will
be sent if the length of the data field is zero.
16 Append header CRC (HC) - Append CRC calculated according to the RMAP specification after the
data sent from the header pointer. The CRC covers all bytes from this pointer except a number of
bytes in the beginning specified by the non-crc bytes field. The CRC will not be sent if the header
length field is zero.
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 87. 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 88. GRSPW transmit descriptor word 2 (address offset 0x8)
31 24 23 0
RESERVED DATALEN
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