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GD32F20x User Manual
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communication system is ideal for applications in which the data traffic is of a periodic nature.
In this mode, the 16-bit internal counter of the CAN hardware is activated and used to
generate the time stamp value stored in the CAN_RFIFOMPx and CAN_TMPx registers for
reception and transmission respectively. The internal counter is incremented each CAN bit
time. The internal counter is captured on the sample point of the SOF (Start of Frame) bit in
both reception and transmission.
The automatic retransmission is disabled in the time-triggered CAN communication.
26.3.7.
Communication parameters
Nonautomatic retransmission mode
This mode has been implemented in order to fulfill the requirement of the time-triggered
communication option of the CAN standard. To configure the hardware in this mode the ARD
bit in the CAN_CTL register must be set.
In this mode, each transmission is started only once. If the first attempt fails, due to an
arbitration loss or an error, the hardware will not automatically restart the frame transmission.
At the end of the first transmission attempt, the hardware considers the request as finished
and sets the MTF bit in the CAN_TSTAT register. The result of the transmission is indicated
in the CAN_TSTAT register by the MTFNERR, MAL and MTE bits.
Bit time
On the bit-level the CAN protocol uses synchronous bit transmission. This not only enhances
the transmitting capacity but also means that a sophisticated method of bit synchronization is
required. While bit synchronization in a character-oriented transmission (asynchronous) is
performed upon the reception of the start bit available with each character, a synchronous
transmission protocol there is just one start bit available at the beginning of a frame. To ensure
the receiver to correctly read the messages, continuous resynchronization is required. Phase
buffer segments are therefore inserted before and after the nominal sample point within a bit
interval.
The CAN protocol regulates bus access by bit-wise arbitration. The signal propagation from
sender to receiver and back to the sender must be completed within one bit-time. For
synchronization purposes a further time segment, the propagation delay segment, is needed
in addition to the time reserved for synchronization, the phase buffer segments. The
propagation delay segment takes into account the signal propagation on the bus as well as
signal delays caused by transmitting and receiving nodes.
The normal bit time simplified by the CAN from the CAN protocol has three segments as
follows:
Synchronization segment (SYNC_SEG)
: a bit change is expected to occur within this time
segment. It has a fixed length of one time quantum (
1 × 𝑡
𝐶𝐴𝑁
).
Содержание GD32F20 Series
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Страница 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
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Страница 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
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Страница 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...