National CP3BT26 - Manual (Page 136)

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CP3BT26
TSEG1 The Time Segment 1 field configures the
length of the Time Segment 1 (TSEG1). It is
not recommended to configure the time seg-
ment 1 to be smaller than 2 time quanta. (see
Table 59).
TSEG2 The Time Segment 2 field specifies the num-
ber of time quanta (tq) for phase segment 2
(see Table 60).
19.10.8 Global Mask Register (GMSKB/GMSKX)
The GMSKB and GMSKX registers allow software to global-
ly mask, or “don’t care” the incoming extended/standard
identifier bits, RTR/XRTR and IDE. Throughout this docu-
ment, the GMSKB and GMSKX 16-bit registers are refer-
enced as a 32-bit register GMSK.
The following are the bits for the GMSKB register.
The following are the bits for the GMSKX register.
For all GMSKB and GMSKX register bits, the following ap-
plies:
0 – The incoming identifier bit must match the correspond-
ing bit in the message buffer identifier register.
1 – Accept 1 or 0 (“don’t care”) in the incoming ID bit inde-
pendent from the corresponding bit in the message
buffer ID registers. The corresponding ID bit in the mes-
sage buffer will be overwritten by the incoming identifier
bits.
When an extended frame is received from the CAN bus, all
GMSK bits GM[28:0], IDE, RTR, and XRTR are used to
mask the incoming message. In this case, the RTR bit in the
GMSK register corresponds to the SRR bit in the message.
The XRTR bit in the GMSK register corresponds to the RTR
bit in the message.
During the reception of standard frames only the GMSK bits
GM[28:18], RTR, and IDE are used. In this case, the
GM[28:18] bits in the GMSK register correspond to the
ID[10:0] bits in the message.
Table 59 Time Segment 1 Settings
TSEG1[3:0]
Length of Time
(TSEG1)
0000 Not recommended
0001 2 time quanta
0010 3 time quanta
0011 4 time quanta
0100 5 time quanta
0101 6 time quanta
0110 7 time quanta
0111 8 time quanta
1000 9 time quanta
1001 10 time quanta
1010 11 time quanta
1011 12 time quanta
1100 13 time quanta
1101 14 time quanta
1110 15 time quanta
1111 16 time quanta
Table 60 Time Segment 2 Settings
TSEG2 Length of TSEG2
000 1 time quantum
001 2 time quanta
010 3 time quanta
011 4 time quanta
100 5 time quanta
101 6 time quanta
110 7 time quanta
111 8 time quanta
15 5 4 3 2 0
GM[28:18] RTR IDE GM[17:15]
0
R/W
15 1 0
GM[14:0] XRTR
0
R/W
Global Mask GM[28:18] RTR IDE GM[17:0] XRTR
Standard
Frame
ID[10:0] RTR IDE Unused
Extended
Frame
ID[28:18] SRR IDE ID[17:0] RTR