Received UDP datagram while sending a UDP datagram causes conflict

[Phonog]

Hi, I am using a e-ink display board from the Soldered company model Inkplate6Motion which uses an ESP32C3 as a coprocessor for wifi communication. The board is supplied with a library that handles the communication between the main processor (STM32H7) and the ESP32 using SPI-AT. The library does not request the firmware version so I am unable to mention it here.
The issue is the following (at least seems to be so, after having added to the library a few println to track the execution flow):
Normal operation:
The udp.write() function prepares the ESP32 to send a datagram. After the AT command is sent to put the ESP32 to sending mode, the library waits for the handshake signal, then checks if the SPI is in "ready to write" mode, then the library sends the contents of the datagram and the udp frame is sent over wifi.
abnormal operation:
at the time the write() function waits for the handshake signal, an incomoing udp frame arrives. Then the handshake signal rises, and the write() function checks the SPI state, but this time it is "ready to read", requesting attention to the received frame. Then the library function write() returns with an error state since it expected a "ready to write" state.
Is this a flaw in the library, or in the SPI-AT specification? Or should the library at all times, including when writing, be able to read an incoming frame, then resume the sending process?

[Jacques-Zhao]

According to the design of SPI AT(https://docs.espressif.com/projects/esp-at/en/latest/esp32c3/Compile_and_Develop/How_to_implement_SPI_AT.html#handshake-pin), the slave read and write are linear and cannot be carried out simultaneously. When both read and write occur at the same time, the slave will arbitrate the subsequent actions. In your scenario, the slave has already indicated that it needs to perform a read operation first. Therefore, the master must first read the data, and then the slave will again send an interruption notification to the master to indicate that it is ready to write data.

[Phonog]

Thank you very much for this clarification.