ST10F273Z4 STMicroelectronics, ST10F273Z4 Datasheet - Page 180

• Manufacturer Part Number: ST10F273Z4
• Description: 16-BIT MICROCONTROLLER WITH MAC UNIT, UP TO 832 KBYTES FLASH MEMORY AND UP TO 68 KBYTES RAM
• Manufacturer: STMicroelectronics

Specifications of ST10F273Z4

• Single Voltage Supply: 5 V ±10%

Known limitations
25.1.2
25.1.3
180/188
Concurrent transmission requests in DAR-mode (C-CAN module)
Description
When the C-CAN module is configured to operate in DAR mode (Disable Automatic
Retransmission) and the host requests the transmission of several messages at the same
time, only two of these messages are transmitted. For all other message transmission
requests the TxRqst bits are reset, no transmission is started, and NewDat and IntPnd are
kept unchanged. For the two messages which are transmitted, the TxRqst and NewDat bits
are reset and IntPnd is set if if it has been enabled by TxIE. TxRqst, NewDat and IntPnd are
bits of the message interface control registers.
The normal operation mode (DAR = 0) is not affected by this phenomenon.
Workaround
The DAR mode is intended to support time-triggered operation (TTCAN level 1) supporting
the transmission of a message only in its dedicated time window. It is an error to request the
transmission of several messages at the same time, and no workarounds should
consequently be necessary for TTCAN applications.
The progress of a requested transmission can be monitored by checking the message
object TxRqst and NewDat [optionally IntPnd] bits. In DAR mode, when a message
transmission has failed either because the transmission was disturbed or because it has not
started, it is necessary to request the message transmission again.
For details on DAR mode and message control registers, refer to user manual UM0409.
Disabling the transmission requests (C-CAN module)
Description
If the host disables the pending transmission request of the lowest-priority message
(number 32 by default) in the short time window during which the message handler state
machine prepares the transmission, but before the transmission has actually started, then
this transmission request may remain disabled. It remains in this state even if the host
immediately re-enables it.
The status of the message object transmission request bit does not show that the
transmission is disabled. This only happens when the message object is the only one with a
pending transmission request.
If the transmission request is blocked in the disabled state, it will be re-enabled by the first
activity detected on the CAN bus or by setting the transmission request of any other
message object.
The other message objects are not affected by this phenomenon.
Workaround
It is usually not necessary to disable the transmission request of a message object. If the
message object is to be used for another message, it is sufficient to prepare the new content
corresponding to this message in the CPU interface register (Identifier, DLC, Data, with
TxRqst and NewDat [optionally TxIE] bits) and to transfer it into the message object. The
new content is then transmitted at the next opportunity, and is not altered by a possibly
ongoing transmission of the previous content of the same message object.
ST10F273Z4