FT260Q-R datasheet(26/61 Pages) FTDI

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FT260 HID-CLASS USB TO UART/I2C BRIDGE IC

Version 1.1

Document No.: FT_001272 Clearance No.: FTDI#484

5.3.3 UART Flow Control

The UART interface needs to implement proper flow control to prevent data from being lost by the

external device. This will be done using either hardware or software flow control. The FT260 UART

supports the modes listed below.



OFF, and switch UART pins to GPIO



RTS_CTS mode (hardware flow control)



DTR_DSR mode (hardware flow control)



XON_XOFF (software flow control)



No flow control mode

RTS/CTS Hardware Flow Control

When RTS / CTS flow control is used, the CTS input indicate to the FT260 that the data communications

equipment (DCE) is ready to receive data. If it is active (low), then the FT260 is free to transmit data on

the TX data line, otherwise it has to hold the data until CTS goes low. The RTS output is used to indicate

that The FT260 is capable of receiving data (active low). Thus, it should be set inactive by the FT260

when both the UART receive register and receive holding register are full.

DTR/DSR Hardware Flow Control

These signals are provided to give information about the status of each UART. When this mode is enabled

and the DTS input is high, the FT260 UART should not send any data on the TX line. DTR will be enabled

on reset and a register bit will allow the IO Bus to alter the state at any time.

Software Flow Control

When software flow control is enabled the XON character and XOFF character are used to stop and start

the flow of data. The XON character tells the downstream device to start sending data. The XOFF

character tells the downstream device to stop sending data. Typical defaults for XON is `11’ and for XOFF

is `13’.

5.3.4 UART Timing

Figure 5.8 UART Timing

Parameter

Min(ns)

Typ(ns)

Max(ns)

Description

T0@48MHz

-2500ppm

20.833

+2500ppm

T0 is the period when operating clock=48MHz

4*T0

40000*T0

Baud clock period of txd

Table 5.4 UART Timing

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