Command Register; Table 22-4. Cmr Register; Table 22-5. Cmr Register Definitions - Sharp Blue Treak LH75400 User Manual

LH75400/01/10/11 (Preliminary) User's Guide

22.3.2.2 Command Register

CMR is the Command Register. The active bits used in this register are Write Only. Setting
one or more of the usable bits starts an action in the CAN Controller's transfer layer. Writ-
ing a 0 to any bit has no effect.
When using this register:
• All bits return 0 when this register is read.
• At least one system clock cycle is needed between consecutive commands.
• Setting bits [1] and [0] simultaneously results in single-shot transmission of the transmit
message without re-transmission in case an error or loss of arbitration occurs.
• Setting bits [4] and [1] simultaneously results in a single-shot transmission of the
Transmit message using the Self-Reception feature, again without re-transmission in
case of an error or arbitration loss.
• If bits [4] and [0] are set simultaneously, bit [4] is ignored.
• A transmission request made in a previous command cannot be cancelled by setting bit
[0] to 0. The requested transmission can only be cancelled by setting bit [1] to 1.
BIT
FIELD
RESET
RW
BIT
FIELD
RESET
RW
ADDR
BIT NAME
31:5
4 SRR
3 CDO
2 RRB
1
0
31 30 29 28 27
0 0 0 0
R R R R R
15 14 13 12 11
0 0 0 0
R R R R R

Table 22-5. CMR Register Definitions

/// Reserved Writing to these bits has no effect. Reading returns 0.
Self-Reception Request
0 = No message is transmitted or received simultaneously.
1 = A message is transmitted and received simultaneously.
Clear Data Overrun
0 = Do not clear the data overrun condition signaled by the Data Overrun Status bit in the
Status Register.
1 = Clear the data overrun condition signaled by the Data Overrun Status bit (bit [1] of the
Status Register, described in Section 22.3.2.3).
Note that no further data overrun interrupt is generated while the Data Overrun Status bit
remains set.
Release Receive Buffer
0 = Do not release the Receive Buffer.
1 = Release the Receive Buffer.
Abort Transmission
AT
0 = Do not cancel the next transmission request.
1 = Cancel the next transmission request, provided it is not already in progress.
Transmission Request
TR
0 = No message is to be transmitted.
1 = A message is to be transmitted.

Table 22-4. CMR Register

26 25 24 23
///
0 0 0 0 0
R R R R
10 9 8 7
///
0 0 0 0 0
R R R R
0xFFFC5000 + 0x04
DESCRIPTION
6/17/03
Controller Area Network
22 21 20 19 18
0 0 0 0 0
R R R R R
6 5 4 3 2
SRR CDO RRB
0 0 0 0 0
R R W W W
17 16
0 0
R R
1 0
AT TR
0 0
W W
22-9