MC68376BGMAB20 Freescale Semiconductor, MC68376BGMAB20 Datasheet - Page 271

• Manufacturer Part Number: MC68376BGMAB20
• Description: IC MCU 32BIT 8K ROM 160-QFP
• Manufacturer: Freescale Semiconductor
• Series: M683xxr

Specifications of MC68376BGMAB20

• Core Processor: CPU32
• Core Size: 32-Bit
• Speed: 20MHz
• Connectivity: CAN, EBI/EMI, SCI, SPI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 18
• Program Memory Type: ROMless
• Ram Size: 7.5K x 8
• Voltage - Supply (vcc/vdd): 4.75 V ~ 5.25 V
• Data Converters: A/D 16x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 160-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

13.5.4.2 Locking and Releasing Message Buffers
13.5.5 Remote Frames
MC68336/376
USER’S MANUAL
The lock/release/busy mechanism is designed to guarantee data coherency during the
receive process. The following examples demonstrate how the lock/release/busy
mechanism will affect TouCAN operation.
Polling the control/status word of a receive message buffer can lock it, preventing a
message from being transferred into that buffer. If the control/status word of a receive
message buffer is read, it should then be followed by a read of the control/status word
of another buffer, or by reading the free-running timer, to ensure that the locked buffer
is unlocked.
The remote frame is a message frame which is transmitted to request a data frame.
The TouCAN can be configured to transmit a data frame automatically in response to
a remote frame, or to transmit a remote frame and then wait for the responding data
frame to be received.
When transmitting a remote frame, the user initializes a message buffer as a transmit
message buffer with the RTR bit set to one. Once this remote frame is transmitted suc-
cessfully, the transmit message buffer automatically becomes a receive message buff-
er, with the same ID as the remote frame which was transmitted.
When a remote frame is received by the TouCAN, the remote frame ID is compared
to the IDs of all transmit message buffers programmed with a code of 1010. If there is
an exact matching ID, the data frame in that message buffer is transmitted. If the RTR
1. Reading a control/status word of a message buffer triggers a lock for that
2. To release a locked message buffer, the CPU32 either locks another message
3. If a receive frame with a matching ID is received during the time the message
4. When a locked message buffer is released, if a frame with a matching identifier
5. If two or more receive frames with matching IDs are received while a message
6. If the user reads the control/status word of a receive message buffer while a
message buffer. A new received message frame which matches the message
buffer cannot be written into this message buffer while it is locked.
buffer by reading its control/status word, or globally releases any locked
message buffer by reading the free-running timer.
buffer is locked, the receive frame will not be immediately transferred into that
message buffer, but will remain in the serial message buffer. There is no indi-
cation when this occurs.
exists within the serial message buffer, then this frame will be transferred to the
matching message buffer.
buffer with a matching ID is locked, the last received frame with that ID is kept
within the serial message buffer, while all preceding ones are lost. There is no
indication when this occurs.
frame is being transferred from a serial message buffer, the BUSY code will be
indicated. The user should wait until this code is cleared before continuing to
read from the message buffer to ensure data coherency. In this situation, the
read of the control/status word will not lock the message buffer.
CAN 2.0B CONTROLLER MODULE (TouCAN)
MOTOROLA
13-15