TL16CP754CPMRG4 datasheet(11/49 Pages) TI

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UART 1

Parallel to Serial

Serial to Parallel

Xon-1 Word

Xon-2 Word

Xoff-1 Word

Transmit

FIFO

Serial to Parallel

Parallel to Serial

Xon-1 Word

Xon-2 Word

Xoff-1 Word

Xoff-2 Word

Receive

FIFO

Data

Xoff - Xon - Xoff

Compare

Programmed

Xon- Xoff

Characters

UART 2

TL16CP754C, TL16CM754C, TL16C754C

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SLLS644E – DECEMBER 2007 – REVISED MAY 2010

Figure 4. Software Flow Control Example

Software Flow Control Example

Assumptions: UART1 is transmitting a large text file to UART2. Both UARTs are using software flow control with

single character Xoff (0F) and Xon (0D) tokens. Both have Xoff threshold (TCR [3:0]=F) set to 60 and Xon

threshold (TCR[7:4]=8) set to 32. Both have the interrupt receive threshold (TLR[7:4]=D) set to 52.

UART1 begins transmission and sends 52 characters, at which point UART2 generates an interrupt to its

processor to service the RCV FIFO, but assumes the interrupt latency is fairly long. UART1 continues sending

characters until a total of 60 characters have been sent. At this time UART2 will transmit a 0F to UART1,

informing UART1 to halt transmission. UART1 will likely send the 61st character while UART2 is sending the Xoff

character. Now UART2 is serviced and the processor reads enough data out of the RCV FIFO that the level

drops to 32. UART2 now sends a 0D to UART1, informing UART1 to resume transmission.

Reset

Table 2 summarizes the state of outputs after reset.

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Product Folder Link(s): TL16CP754C TL16CM754C TL16C754C

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