CR16MCS9VJE8 National Semiconductor, CR16MCS9VJE8 Datasheet - Page 152

• Manufacturer Part Number: CR16MCS9VJE8
• Description: 16-Bit Microcontroller IC
• Manufacturer: National Semiconductor

Specifications of CR16MCS9VJE8

• Controller Family/series: CR16X
• Core Size: 16 Bit
• Program Memory Size: 64K X 8 Flash
• Digital Ic Case Style: PQFP
• No. Of Pins: 80
• Mounting Type: Surface Mount
• Clock Frequency: 25MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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26.0 Appendix
The following document describes problems identified in the
CR16 modules.
26.1
26.1.1
Under certain conditions it occurs that the CR16CAN module
receives a frame, sent by itself even though the loopback fea-
ture is disabled.
This condition consists of two parts, which both must be true
to cause this malfunction.
A) The first part is that a transmit buffer and at least one re-
ceive buffer are configured with the same identifier. Let's call
this identifier ID_RX_TX here. With regard to the receive
buffer, this means that the buffer identifier and the corre-
sponding filter masks are setup in a way that the buffer is able
to receive frames with the identifier ID_RX_TX.
B) The second part is that the CAN communication must take
place in the following sequence:
After this communication the frame sent by the CR16CAN
module will be copied into the next receive buffer available
for the identifier ID_RX_TX.
Note: If a frame with an identifier different to ID_RX_TX is
sent or received in between the steps 1 and 2, the problem
does not occur.
26.1.2
When a frame is received into the hidden receive buffer, the
CR16CAN module scans through all CAN message buffers.
During this sequence all receive buffers (RX-buffers) capable
of receiving this frame are tagged (RX-tag). If the message
was received correctly the frame is copied into first tagged
buffer (lowest buffer number).
Every CAN node also monitors frames being transmitted in
order to switch from transmitter to receiver after a lost arbitra-
tion. In order to do this the CR16CAN module also receives
transmitted frames into the hidden receive buffer.
The scanning sequence is also applied to transmitted
frames. This means, the identifier in the hidden receive buffer
is compared with the RX-buffer identifiers. As the identifier is
the same as with the last receive scanning sequence, the
RX-tags will not be changed.
A CAN buffer receive tag is only updated in the following cas-
es:
1. A message with the identifier ID_RX_TX from another
2. A message with the identifier ID_RX_TX is sent by the
— A new scanning sequence has overwritten the old re-
— The CPU has changed the CAN buffer status in the
— The CPU has changed the CAN buffer identifier.
CAN node is received into the receive buffer.
CR16CAN module immediately after the reception took
place (Note).
ceive tags due to a different identifier mask under com-
parison.
CNSTAT.ST-field to any value which disables the buff-
er to receive a message (e.g. RX_NOT_ACTIVE or
any TX-state)
CR16CAN Problem Descriptions:
CR16CAN Problem Cause
CR16CAN
152
Applied to the CAN communication sequence described
above, this means that the transmitted message, currently
present in the hidden receive buffer will be copied into the
same receive buffer and the message received from the oth-
er CAN node will be overwritten.
Example
Buffer Settings
CAN Communication Sequence A:
(BUFFLOCK disabled)
Note: 1. Step 2 does not need to be done. In case the buffer
1 status is not updated to RX_READY, the buffer status will
change from RX_FULL to RX_OVERRUN in step 4.
Note: 2. As BUFFLOCK is disabled, all messages with the
identifier ID_RX_TX will be copied into buffer 1. Buffer 2 does
not receive any message.
CAN Communication Sequence B:
(BUFFLOCK enabled)
CAN Communication Sequence C
(CR16CAN does NOT receive a frame sent by itself.)
X = don't care
1. Message sent from another CAN node received into
2. CPU reads out data from CAN buffer 1 and resets the
3. CAN buffer 0 sends a frame (status set to TX_ONCE).
4. Status of CAN buffer 1 changes to RX_FULL, because it
1. Message sent from another CAN node received into
2. CAN buffer 0 sends a frame.
3. Status of CAN buffer 2 changes to RX_FULL, because it
Number
Buffer
Filter Masks:
GMSKB = 0x0000
GMSKX = 0x000F
Buffer configuration:
CAN
buffer 1.
Buffer 1 and buffer 2 are tagged for reception of this
message.
buffer state from RX_FULL to RX_READY (Note 1).
has received the message sent by buffer 0 (Note 2).
buffer 1. Buffer 1 is locked now.
Buffer 1 and buffer 2 are tagged for reception of this
message.
has received the message sent by buffer 0.
0
1
2
3
TX_NOT_ACTIVE 0x15555550 0x1555555X
CAN Buffer
RX_READY
RX_READY
RX_READY
Status
0x15555551 0x1555555X
0x15555552 0x1555555X
0x15555003 0x1555500X
Identifier
Buffer
Identifier
Mask