Visible to Intel only — GUID: zoc1662687920221
Ixiasoft
Visible to Intel only — GUID: zoc1662687920221
Ixiasoft
55.2.4. Handshaking Signal (CTS/RTS Flow Control)
When Lightweight UART core acts as a transmitter, you should assert rts_n by writing to RTS bit of control register at address offset 0x3 to request for data transmission. You should monitor the cts_n signal by reading CTS bit of status register at address offset 0x2 to check if the core is allowed to send data to the other device. Data transmission will take place when the Lightweight UART Core receives asserted cts_n signal. Txdata that have been written into TXFIFO will be shifted out via TXD stream.
As described in the following figure, if data transmission has been stopped by cts_n signal deasserted by the other device, the transmit shift register will stop loading the next txdata from the TXFIFO until cts_n is asserted again. Note that the core will still continue to shift out the remaining bits of the txdata that has been loaded in transmit shift register via TXD stream until the transmit shift register is empty. You can de-assert rts_n when transmit data empty bit of status register is HIGH to indicate the completion of data transfer.
When the Lightweight UART core acts as a receiver, before asserting rts_n, you should read the RXFIFO almost full bit of status register at address offset 0x2 to check if the Lightweight UART core is ready to accept new data from RXD stream.
As described in the following figure, during data transmission, when RXFIFO hits almost full, the Lightweight UART Core will de-assert rts_n automatically to halt data transmission to indicate that the core is not ready to accept new data. You should read out rxdata from RXFIFO in order to resume data transmission process. When the core detect RXFIFO is not almost full, the IP will re-assert back rts_n automatically to accept new data. The remaining RXFIFO depth to assert almost full status can be configurable in GUI.