Espressif ESP32 Technical Reference Manual page 550

21 Two-wire Automotive Interface (TWAI)
Error Frame
Error Flag Superposition
Error Delimeter
Overload Frames
An Overload Frame has the same bit fields as an Error Frame containing an Active Error Flag. The key difference
is in the conditions that can trigger the transmission of an Overload Frame. Figure
fields of an Overload Frame.
Overload Frame
Overload Flag
Overload Flag Superposi-
tion
Overload Delimeter
Overload Frames will be transmitted under the following conditions:
1. The internal conditions of a Receiver requires a delay of the next Data or Remote Frame.
2. Detection of a Dominant bit at the first and second bit of Intermission.
3. If a Dominant bit is detected at the eighth (last) bit of an Error Delimeter. Note that in this case, TEC and
REC will not be incremented (See Section 21.3.3).
Transmitting an overload frame due to one of the conditions must also satisfy the following rules:
• Transmitting an Overload Frame due to condition 1 must only be started at the first bit of Intermission.
• Transmitting an Overload Frame due to condition 2 and 3 must start one bit after the detecting the Dominant
bit of the condition.
• A maximum of two Overload frames may be generated in order to delay the next Data or Remote Frame.
Espressif Systems
Description
The Error Flag Superposition field meant to allow for other nodes on the
bus to transmit their respective Active Error Flags. The superposition
field can range from 0 to 6 bits, and ends when the first Recessive bit is
detected (i.e., the first it of the Delimeter).
The Delimeter field marks the end of the Error/Overload Frame, and con-
sists of 8 Recessive bits.
Figure 21-3. The Bit Fields of an Overload Frame
Table 21-3. Overload Frame
Description
Consists of 6 Dominant bits. Same as an Active Error Flag.
Allows for the superposition of Overload Flags from other nodes, similar
to an Error Flag Superposition.
Consists of 8 Recessive. Same as an Error Delimeter.
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21-3 below shows the bit
ESP32 TRM (Version 5.2)