Intel 8XC196K Series User Manual page 547

8XC196K x, J x , CA USER'S MANUAL
CAN_MSGxCON1
CAN_MSG x CON1
x = 1–15 (87C196CA)
The CAN message object x control 1 (CAN_MSG x CON1) register indicates whether a message
object has been updated, whether a message has been overwritten, whether the CPU is updating the
message, and whether a transmission or reception is pending.
This register consists of four bit-pairs — the most-significant bit of each pair is in true form and the
least-significant bit is in complement form. This format allows software to set or clear any bit with a
single write operation, without affecting the remaining bits.
7
87C196CA
RMTPND
Bit Bit
Number Mnemonic
7:6 RMTPND
5:4 TX_REQ
3:2 MSGLST or
CPUUPD
C-20
RMTPND TX_REQ TX_REQ
Remote Request Pending
Receive message objects do not use this bit-pair.
The CAN controller sets this bit-pair to indicate that a remote frame has
requested the transmission of a transmit message object. If the CPUUPD
bit-pair is clear, the CAN controller transmits the message object, then
clears RMTPND. Setting RMTPND does not cause a transmission; it only
indicates that a transmission is pending.
bit 7 bit 6
0 1 no pending request
1 0 a remote request is pending
Transmission Request
Set this bit-pair to cause a receive message object to transmit a remote
frame (a request for transmission) or to cause a transmit object to transmit
a data frame. Read this bit-pair to determine whether a transmission is in
progress.
bit 5 bit 4
0 1 no pending request; no transmission in progress
1 0 transmission request; transmission in progress
Message Lost (receive)
For a receive message object, the CAN controller sets this bit-pair to
indicate that it stored a new message while the NEWDAT bit-pair was still
set, overwriting the previous message.
bit 3 bit 2
0 1 no overwrite occurred
1 0 a message was lost (overwritten)
CPU Updating (transmit)
For a transmit message object, software should set this bit-pair to indicate
that it is in the process of updating the message contents. This prevents a
remote frame from triggering a transmission that would contain invalid
data.
bit 3 bit 2
0 1 the message is valid
1 0 software is updating data
Address:
Reset State:
MSGLST MSGLST
NEWDAT
CPUUPD CPUUPD
Function
Table C-6
0
NEWDAT