MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 589

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

16.3.1.5 Message Buffer Activation/Deactivation Mechanism
16.3.1.6 Message Buffer Lock/Release/Busy Mechanism
16.3.2 Receive Mask Registers
MPC555
USER’S MANUAL
Each message buffer must be activated once the user configures it for the desired op-
eration. A buffer is activated by writing the appropriate code to the control/status word
for that buffer. Once the buffer is activated, it will begin participating in the normal
transmit and receive processes.
A buffer is deactivated by writing the appropriate deactivation code to the control/sta-
tus word for that buffer. A buffer is typically deactivated when the user desires to re-
configure the buffer (for example to change the buffer’s function from Rx to Tx or Tx to
Rx). The buffer should also be deactivated before changing a receive buffer’s mes-
sage identifier or before loading a new message to be transmitted into a transmit buff-
er.
For more details on activation and deactivation of message buffers and the effects on
message buffer operation, refer to
In addition to the activation/deactivation mechanism, the TouCAN also uses a lock/re-
lease/busy mechanism to ensure data coherency during the receive process. The
mechanism includes a lock status for each message buffer and uses the two serial
message buffers to facilitate frame transfers within the TouCAN.
Reading the control/status word of a receive message buffer triggers the lock for that
buffer. While locked, a received message cannot be transferred into that buffer from
one of the serial message buffers.
If a message transfer between the message buffer and a serial message buffer is in
progress when the control/status word is read, the BUSY status is indicated in the
code field, and the lock is not activated.
The user can release the lock on a message buffer in one of two ways. Reading the
control/status word of another message buffer locks that buffer, releasing the previ-
ously locked buffer. A global release can also be performed on any locked message
buffer by reading the free-running timer.
Once a lock is released, any message transfers between a serial message buffer and
a message buffer that were delayed due to that buffer being locked will take place. For
more details on the message buffer locking mechanism, and the effects on message
buffer operation, refer to
The receive mask registers are used as acceptance masks for received frame IDs.
The following masks are defined:
The value of the mask registers should not be changed during normal operation. If the
mask register data is changed after the masked identifier of a received message is
• A global mask, used for receive buffers 0-13
• Two separate masks for buffers 14 and 15
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MPC556
16.4 TouCAN
CAN 2.0B CONTROLLER MODULE
Rev. 15 October 2000
16.4 TouCAN
Operation.
Operation.
MOTOROLA
16-7