Can Reset Mode; Table 22-38. Effect Of Reset On Can Controller Registers - Sharp Blue Treak LH75400 User Manual

Controller Area Network

22.3.3 CAN Reset Mode

There are two ways for the CAN Controller to enter Reset Mode:
• Setting the Reset Mode bit in the Mode Register (see Section 22.3.2.1) so that the cur-
rent transmission/reception of any message is aborted. This causes the CAN Controller
to enter Reset Mode on the next positive edge of the system clock.
• Going to Bus Off state (bit [7] of the Status Register set to 1) following a System Reset.
This situation occurs, for example, when the transmit error counter exceeds its maxi-
mum count of 255.
To return the CAN Controller to Operating Mode, clear the Reset Mode bit (bit [0] of the
Mode Register. The CAN Controller does not send or receive any data until it detects either:
• A Bus Free sequence of 11 recessive bits on the bus, if the reset was triggered by
a System Reset.
• 128 such sequences, if the reset was caused by the bus status going to Bus Off.
Table 22-38 describes the effect of the reset on the CAN Controller registers. In this table,
'x' means the reset has no effect on the value of these registers or bits.

Table 22-38. Effect of Reset on CAN Controller Registers

REGISTER
Mode
Command
Status
22-30
BIT SYMBOL
7:5 Reserved
4 Reserved
3 AFM Acceptance Filter Mode
2 STM Self Test Mode
1 LOM Listen Only Mode
0 RM Reset Mode
7:5 Reserved
4 SRR Self-Reception Request
3 CDO Clear Data Overrun
2 RRB Release Receive Buffer
1 AT Abort Transmission
0 TR Transmission Request
7 BS Bus Status
6 ES Error Status
5 TS Transmit Status
4 RS Receive Status
3 TCS Transmission Complete Status
2 TBS Transmit Buffer Status
1 DOS Data Overrun Status
0 RBS Receive Buffer Status
6/17/03
LH75400/01/10/11 (Preliminary) User's Guide
NAME
SYSTEM
0 (reserved)
0 (reserved)
0 (dual filters)
0 (normal)
0 (normal)
1 (present)
0 (reserved)
0 (absent)
0 (no action)
0 (no action)
0 (absent)
0 (absent)
0 (bus-on)
0 (ok)
1 (wait idle)
1 (wait idle)
1 (complete)
1 (released)
0 (absent)
0 (empty)
RESET VALUE
NOTES
SOFTWARE
0 (reserved)
0 (reserved)
x
x
x
1 (present)
0 (reserved)
0 (absent)
0 (no action)
0 (no action)
0 (absent)
0 (absent)
x
x
1 (wait idle)
1 (wait idle)
X
1 (released)
0 (absent)
0 (empty)
1