NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 781 -
Revision V1.30
NUC97
0
T
E
CHNIC
A
L
RE
F
E
RE
N
CE
MA
NUA
L
arbitration and control field (Iden IDE + RTR + DLC) from the shift register is stored in the
Message Object of the Message RAM and the NewDat bit of this Message Object is set. The data field
of the Message Object remains unchanged; the Remote Frame is treated similar to a received Data
Frame.
Receive/Transmit Priority
5.24.7.6
The receive/transmit priority for the Message Objects is attached to the message number. Message
Object 1 has the highest priority, while Message Object 32 has the lowest priority. If more than one
transmission request is pending, they are serviced due to the priority of the corresponding Message
Object
Configuring a Transmit Object
5.24.7.7
The following table shows how a Transmit Object should be initialized.
Ms
A
rb
D
a
ta
Mas
k
E
oB
D
ir
N
e
wD
a
t
MsgLst
R
x
IE
TxIE
Int
P
n
d
R
m
tE
n
TxR
qst
1
appl.
appl.
appl.
1
1
0
0
0
appl.
0
appl.
0
Table 5.24-1 Initialization of a Transmit Object
Note:
appl. = application software.
The Arbitration Register values (ID28-0 and Xtd bit) are provided by the application. They define the
identifier and type of the outgoing message. If an 11-
bit Identifier (“Standard Frame”) is used, it is
programmed to ID28 - ID18. The ID17 - ID0 can then be disregarded.
If the TxIE bit is set, the IntPnd bit will be set after a successful transmission of the Message Object.
If the RmtEn bit is set, a matching received Remote Frame will cause the TxRqst bit to be set; the
Remote Frame will autonomously be answered by a Data Frame.
The Data Register values (DLC3-0, Data0-7) are provided by the application, TxRqst and RmtEn may
not be set before the data is valid.
The Mask Registers (Msk28-
0, UMask, MXtd, and MDir bits) may be used (UMask=’1’) to allow groups
of Remote Frames with similar identifiers to set the TxRqst bit. The Dir bit should not be masked.
Updating a Transmit Object
5.24.7.8
The software may update the data bytes of a Transmit Object any time through the IFn Interface
registers, neither MsgVal nor TxRqst have to be reset before the update.
Even if only a part of the data bytes are to be updated, all four bytes of the corresponding IFn Data A
Register or IFn Data B Register have to be valid before the contents of that register are transferred to
the Message Object. Either the application software has to write all four bytes into the IFn Data
Register or the Message Object is transferred to the IFn Data Register before the software writes the
new data bytes.
When only the (eight) data bytes are updated, first 0x0087 is written to the Command Mask Register
and then the number of the Message Object is written to the Command Request Register,
concurrently updating the data bytes and setting TxRqst.