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www.diodes.com

April 2019

Diodes Incorporated

PI7C9X752

Document Number DS40312 Rev 3-2

A product Line of

Diodes Incorporated

PI7C9X752

RX

FIFO

Figure 1. Auto ow control (Auto-RTS and Auto-CTS) example

TX

FIFO

SERIAL TO

PARALLEL

FLOW

CONTROL

PARALLEL

TO SERIAL

FLOW

CONTROL

RX

FIFO

TX

FIFO

SERIAL TO

PARALLEL

FLOW

CONTROL

PARALLEL

TO SERIAL

FLOW

CONTROL

UART 1

UART 2

TX

TX

RX

RX

RTS

RTS

CTS

CTS

2. Hardware Flow Control

Hardware flow control is comprised of Auto-CTS and Auto-RTS (see Figure 1). Auto-CTS and Auto-RTS can be enabled/disabled

independently by programming EFR[7:6].

With Auto-CTS, CTS must be active before the UART can transmit data.

Auto-RTS only activates the RTS output when there is enough room in the FIFO to receive data and de-activates the RTS output when

the RX FIFO is sufficiently full. The halt and resume trigger levels is controlled by FCR and FCTR bits.

If both Auto-CTS and Auto-RTS are enabled, when RTS is connected to CTS, data transmission does not occur unless the receiver

FIFO has empty space. Thus, overrun errors are eliminated during hardware flow control. If not enabled, overrun errors occur if the

transmit data rate exceeds the receive FIFO servicing latency.