GR712RC-UM, Jun 2017, Version 2.9 146 www.cobham.com/gaisler
GR712RC
18.5.12 Transmit buffer
The transmit buffer is write-only and mapped on address 16 to 28. Reading of this area is mapped to
the receive buffer described in the next section. The layout of the transmit buffer depends on whether
a standard frame (SFF) or an extended frame (EFF) is to be sent as seen below.
TX frame information (this field has the same layout for both SFF and EFF frames)
Bit 7 - FF selects the frame format, i.e. whether this is to be interpreted as an extended or standard frame. 1 = EFF, 0 = SFF.
Bit 6 - RTR should be set to 1 for an remote transmission request frame.
Bit 5:4 - are don’t care.
Bit 3:0 - DLC specifies the Data Length Code and should be a value between 0 and 8. If a value greater than 8 is used 8 bytes
will be transmitted.
TX identifier 1 (this field is the same for both SFF and EFF frames)
Bit 7:0 - The top eight bits of the identifier.
TX identifier 2, SFF frame
Bit 7:5 - Bottom three bits of an SFF identifier.
Bit 4:0 - Don’t care.
Table 137.
#Write (SFF) Write(EFF)
16 TX frame information TX frame information
17 TX ID 1 TX ID 1
18 TX ID 2 TX ID 2
19 TX data 1 TX ID 3
20 TX data 2 TX ID 4
21 TX data 3 TX data 1
22 TX data 4 TX data 2
23 TX data 5 TX data 3
24 TX data 6 TX data 4
25 TX data 7 TX data 5
26 TX data 8 TX data 6
27 - TX data 7
28 - TX data 8
Table 138.TX frame information address 16
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
FF RTR - - DLC.3 DLC.2 DLC.1 DLC.0
Table 139.TX identifier 1 address 17
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
ID.28 ID.27 ID.26 ID.25 ID.24 ID.23 ID.22 ID.21
Table 140.TX identifier 2 address 18
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
ID.20ID.19ID.18-----
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