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87C196CB SUPPLEMENT
7-26
CAN_MSG
x
CON1
x
= 1–15 (87C196CB)
Address:
Reset State:
1E
x
1H (
x
= 1–F)
Unchanged
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 0
87C196CB
RMTPND RMTPND TX_REQ TX_REQ
MSGLST
CPUUPD
MSGLST
CPUUPD
NEWDAT NEWDAT
Bit
Number
Bit
Mnemonic
Function
7:6 RMTPND 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
5:4 TX_REQ 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
Figure 7-15. CAN Message Object
x
Control 1 (CAN_MSG
x
CON1) Register