MC68HC05X4 Datasheet, PDF (83/156 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Motorola CAN
Interface to the MC68HC05X4 CPU
TCS — Transmission complete status
This bit is cleared by the MCAN when TR becomes set. When TCS is
set it indicates that the last requested transmission was successfully
completed. If, after TCS is cleared, but before transmission begins, an
abort transmission command is issued then the transmit buffer will be
released and TCS will remain clear. TCS will then only be set after a
further transmission is both requested and successfully completed.
1 = Complete – Last requested transmission successfully
completed.
0 = Incomplete – Last requested transmission not complete.
TBA — Transmit buffer access
When clear, the transmit buffer is locked and cannot be accessed by
the CPU. This indicates that either a message is being transmitted, or
is awaiting transmission. If the CPU writes to the transmit buffer while
it is locked, then the bytes will be lost without this being signalled.
1 = Released – The transmit buffer may be written to by the CPU.
0 = Locked – The CPU cannot access the transmit buffer.
DO — Data overrun
This bit is set when both receive buffers are full and there is a further
message to be stored. In this case the new message is dropped, but
the internal logic maintains the correct protocol. The MCAN does not
receive the message, but no warning is sent to the transmitting node.
The MCAN clears DO when the CPU sets the COS bit in the CCOM
register.
Note that data overrun can also be caused by a transmission, since
the MCAN will temporarily store an outgoing frame in a receive buffer
in case arbitration is lost during transmission.
1 = Overrun – Both receive buffers were full and there was another
message to be stored.
0 = Normal operation.
15-mcan
MOTOROLA
Motorola CAN
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MC68HC05X4 Rev 1.0
83