Table 129: Can Bus Timing Register (Canbtr - 0Xe00X X014); Table 130: Can Error Warning Limit Register (Canewl - 0Xe00X X018); Table 131: Can Status Register (Cansr - 0Xe00X X01C) - Philips LPC2194 User Manual

Philips Semiconductors
ARM-based Microcontroller
Bus Timing Register (CANBTR - 0xE00x x014)
This register controls how various CAN timings are derived from the VPB clock. It can be read at any time, but can only be written
if the RM bit in CANmod is 1. See Table 124 for details on specific CAN channel register address.
Table 130: CAN Bus Timing Register (CANBTR - 0xE00x x014)
CANBTR Name Function
Baud Rate Prescaler. The VPB clock is divided by (this value plus one) to produce
0:9 BRP
the CAN clock.
15:14 SJW The Synchronization Jump Width is (this value plus one) CAN clocks.
The delay from the nominal Sync point to the sample point is (this value plus one)
19:16 TSEG1
CAN clocks.
The delay from the sample point to the next nominal sync point is (this value plus
22:20 TSEG2 one) CAN clocks. The nominal CAN bit time is (this value plus the value in TSEG1
plus 3) CAN clocks.
1: the bus is sampled 3 times (recommended for low to medium speed buses)
23 SAM
0: the bus is sampled once (recommended for high speed buses)
Error Warning Limit Register (CANEWL - 0xE00x x018)
This register sets a limit on Tx or Rx errors at which an interrupt can occur. It can be read at any time, but can only be written if
the RM bit in CANmod is 1. See Table 124 for details on specific CAN channel register address.
Table 131: CAN Error Warning Limit Register (CANEWL - 0xE00x x018)
CANEWL Name Function
During CAN operation, this value is compared to both the Tx and Rx Error Counters.
7:0 EWL If either of these counter matches this value, the Error Status (ES) bit in CANSR is
set.
Status Register (CANSR - 0xE00x x01C)
This register contains three status bytes, in which the bits not related to tranmission are identical to the corresponding bits in the
Global Status Register, while those relating to transmission reflect the status of each of the 3 Tx Buffers. See Table 124 for details
on specific CAN channel register address.
Table 132: CAN Status Register (CANSR - 0xE00x x01C)
CANSR Name Function
0, 8, 16 RBS These bits are identical to the RSB bit in the GSR.
1, 9, 17 DOS These bits are identical to the DOS bit in the GSR.
1: software may write a message into the CANTFI, CANTID, CANTDA, and
TBS1,
CANTDB registers for this Tx Buffer.
2, 10, 18 TBS2,
0: software should not write to any of the CANTFI, CANTID, CANTDA, and
TBS3
CANTDB registers for this Tx Buffer.
TCS1, 1: The previously requested transmission for this Tx Buffer has been successfully
3, 11, 19 TCS2, completed.
TCS3 0: The previously requested transmission for this Tx Buffer is not complete.
CAN Controllers and Acceptance Filter
LPC2119/2129/2292/2294
197
Preliminary User Manual
Reset Value RM Set
0 X
0 X
1100 X
001 X
0 X
Reset Value RM Set
96 =0x60 X
10
Reset Value RM Set
0 0
0 0
1 X
1 0
May 03, 2004