XC164-16 Datasheet, PDF (370/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
TwinCAN Module
Field
Bits Type Description
RMTPND
[15:14] rwh
Low
Remote Pending Flag (used for transmit-objects)
01 No remote node request for a message object
data transmission.
10 Transmission of the message object data has
been requested by a remote node but the data
has not yet been transmitted. When RMTPND
is set, the CAN node controller also sets TXRQ.
RMTPND is automatically reset, when the message
object data has been successfully transmitted.
CFCVAL
[15:0] rwh
High
Message Object Frame Counter Value
CFCVAL contains a copy of the frame counter content
valid for the last correct data transmission or
reception executed for the corresponding message
object.
1) MSGVAL has to be set from ‘01’ to ‘10’ in order to take into account an update of bits XTD, DIR, NODE and
CANPTR.
2) Bit NEWDAT indicates that new data has been written into the data registers of this corresponding message
object. For transmit objects, NEWDAT should be set by software and is reset by the respective CAN node
controller when the transmission is started.
For receive objects, NEWDAT is set by the respective CAN node controller after receiving a data frame with
matching identifier. It has to be reset by software.
When the CAN controller writes new data into the message object, unused message bytes will be overwritten
with non-specified values. Usually, the CPU will clear this bitfield before working on the data and will verify that
the bitfield is still cleared once the CPU has finished working to ensure a consistent set of data. For transmit
objects, the CPU should set this bitfield along with clearing bitfield CPUUPD. This will ensure that, if the
message is actually being transmitted during the time the message is updated by the CPU, the CAN controller
will not reset bitfield TXRQ. In this way, TXRQ is only reset once the actual data has been transferred correctly.
3) While bitfield MSGVAL is set (‘10’) an incoming matching remote frame is taken into account by automatically
setting bitfields TXRQ and RMTPND to ‘10’ (independent from bitfield CPUUPD/MSGLST). The transmission
of a frame is only possible if CPUUPD is reset (‘01’).
4) If a receive object (DIR = ‘0’) is requested for transmission, a remote frame will be sent in order to request a
data frame from another node. If a transmit object (DIR = ‘1’) is requested for transmission, a data frame will
be sent. Bitfield TXRQ will be reset by the CAN controller along with bitfield RMTPND after the correct
transmission of the data frame if bitfield NEWDAT has not been set or after correct transmission of a remote
frame.
Note: For transmitting frames (remote frames or data frames), bitfield
CPUUPD/MSGLST has to be reset.
User’s Manual
TwinCAN_X41, V2.1
21-70
V2.1, 2004-03