Datasheet

Serial to

Parallel

Flow

Control

Parallel to

Serial

Flow

Control

FIFO

Parallel to

Serial

Flow

Control

Serial to

Parallel

Flow

Control

FIFO

D7- D0 D7- D0

UART 1 UART 2

RTS

CTS

RTS

TL16CP754C, TL16C754C

SLLS644G –DECEMBER 2007– REVISED MAY 2011

www.ti.com

A. When CTS is low, the transmitter keeps sending serial data out.

B. When CTS goes high before the middle of the last stop bit of the current byte, the transmitter finishes sending the

current byte, but it does not send the next byte.

C. When CTS goes from high to low, the transmitter begins sending data again.

Figure 2. CTS Functional Timing

Figure 3. Autoflow Control (Auto-RTS and Auto-CTS) Example

Software Flow Control

Software flow control is enabled through the enhanced feature register and the modem control register. Different

combinations of software flow control can be enabled by setting different combinations of EFR[3−0]. Table 1

shows software flow control options.

Two other enhanced features relate to S/W flow control:

• Xon Any Function [MCR(5): Operation resumes after receiving any character after recognizing the Xoff

character.

NOTE

It is possible that an Xon1 character is recognized as an Xon Any character, which could

cause an Xon2 character to be written to the RX FIFO.

• Special Character [EFR(5)]: Incoming data is compared to Xoff2. Detection of the special character sets the

Xoff interrupt {IIR(4)] but does not halt transmission. The Xoff interrupt is cleared by a read of the IIR. The

special character is transferred to the RX FIFO.