GD32F403xx User Manual
613
delay segment and Phase buf fer segment 1 in the CAN standard. Its duration is
programmable f rom 1 to 16 time quanta but it may be automatically leng thened to
compensate f or positive phase drifts due to different f requency of the various nodes of the
network.
Bit segment 2 (BS2)
: It def ines the location of the transmit point. It represents the Phase
buf fer segment 2 in the CAN standard. Its duration is programmable from 1 to 8 time quanta
but it may also be automatically shortened to compensate for negative phase drifts.
The bit time is shown as in the
.
Figure 22-11. The bit time
Sync
segment
Propagation delay
segment
Phase buffer
segment 1
Phase buffer
segment2
Normal Bit Time
CAN
protocol
SYNG_SEG
BIT SEGMENT 1(BS1)
BIT SEGMENT 2(BS2)
CAN
The resynchronization Jump Width (SJW): it can be lengthened or shortened to compensate
f or the Synchronization error of the CAN network node. It is programmable from 1 to 4 time
quanta.
A valid edge is defined as the f irst toggle in a bit time f rom dominant to recessive bus level
bef ore the controller sends a recessive bit.
If a valid edge is detected in BS1, not in SYNC_SEG, BS1 is added up to SJW maximumly,
so that the sample point is delayed.
Conversely, if a valid edge is detected in BS2, not in SYNC_SEG, BS2 is cut down to SJW at
most, so that the transmit point is moved earlier.
Baud rate
The clock of the CAN derives from the APB1 bus. The CAN calculates its baud rate as follow:
𝐵𝑎𝑢𝑑𝑅𝑎𝑡𝑒 =
1
𝑁𝑜𝑟𝑚𝑎𝑙 𝐵𝑖𝑡 𝑇𝑖𝑚𝑒
(22-1)
𝑁𝑜𝑟𝑚𝑎𝑙 𝐵𝑖𝑡 𝑇𝑖𝑚𝑒 = 𝑡
𝑆𝑌𝑁𝐶_𝑆𝐸𝐺
+ 𝑡
𝐵𝑆1
+ 𝑡
𝐵𝑆2
(22-2)
with:
𝑡
𝑆𝑌𝑁𝐶_𝑆𝐸𝐺
= 1 × 𝑡
𝑞
(22-3)
𝑡
𝐵𝑆1
= (1 + 𝐵𝑇. 𝐵𝑆1) × 𝑡
𝑞
(22-4)
𝑡
𝐵𝑆2
= (1 + 𝐵𝑇. 𝐵𝑆2) × 𝑡
𝑞
(22-5)
𝑡
𝑞
= (1 + 𝐵𝑇. 𝐵𝐴𝑈𝐷𝑃𝑆𝐶) × 𝑡
𝑃𝐶𝐿𝐾1
(22-6)
Содержание GD32F403 Series
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