Freescale’s Scalable Controller Area Network (S12MSCANV3)
Module Base + 0x0000
Access: User read/write(1)
7
6
5
4
3
2
1
0
R
RXACT
SYNCH
RXFRM
W
CSWAI
TIME
WUPE
SLPRQ
INITRQ
Reset:
0
0
0
0
0
0
0
1
= Unimplemented
Figure 8-4. MSCAN Control Register 0 (CANCTL0)
1. Read: Anytime
Write: Anytime when out of initialization mode; exceptions are read-only RXACT and SYNCH, RXFRM (which is set by the
module only), and INITRQ (which is also writable in initialization mode)
NOTE
The CANCTL0 register, except WUPE, INITRQ, and SLPRQ, is held in the
reset state when the initialization mode is active (INITRQ = 1 and
INITAK = 1). This register is writable again as soon as the initialization
mode is exited (INITRQ = 0 and INITAK = 0).
Table 8-3. CANCTL0 Register Field Descriptions
Field
Description
7
Received Frame Flag — This bit is read and clear only. It is set when a receiver has received a valid message
RXFRM(1) correctly, independently of the filter configuration. After it is set, it remains set until cleared by software or reset.
Clearing is done by writing a 1. Writing a 0 is ignored. This bit is not valid in loopback mode.
0 No valid message was received since last clearing this flag
1 A valid message was received since last clearing of this flag
6
Receiver Active Status — This read-only flag indicates the MSCAN is receiving a message. The flag is
controlled by the receiver front end. This bit is not valid in loopback mode.
0 MSCAN is transmitting or idle2
RXACT
1 MSCAN is receiving a message (including when arbitration is lost)(2)
5
CAN Stops in Wait Mode — Enabling this bit allows for lower power consumption in wait mode by disabling all
CSWAI(3) the clocks at the CPU bus interface to the MSCAN module.
0 The module is not affected during wait mode
1 The module ceases to be clocked during wait mode
4
Synchronized Status — This read-only flag indicates whether the MSCAN is synchronized to the CAN bus and
able to participate in the communication process. It is set and cleared by the MSCAN.
0 MSCAN is not synchronized to the CAN bus
SYNCH
1 MSCAN is synchronized to the CAN bus
3
Timer Enable — This bit activates an internal 16-bit wide free running timer which is clocked by the bit clock rate.
If the timer is enabled, a 16-bit time stamp will be assigned to each transmitted/received message within the
active TX/RX buffer. Right after the EOF of a valid message on the CAN bus, the time stamp is written to the
highest bytes (0x000E, 0x000F) in the appropriate buffer (see Section 8.3.3, “Programmer’s Model of Message
Storage”). The internal timer is reset (all bits set to 0) when disabled. This bit is held low in initialization mode.
0 Disable internal MSCAN timer
TIME
1 Enable internal MSCAN timer
S12P-Family Reference Manual, Rev. 1.13
Freescale Semiconductor
257
FREESCALE [ Freescale ]
