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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

3.1 Receive Flow Control

When software flow control operation is enabled, UART will compare incoming data with Xoff1/Xoff2 programmed characters (in

certain cases, Xoff1 and Xoff2 must be received sequentially). When the correct Xoff characters are received, transmission is halted

after completing transmission of the current character. Xoff detection also sets ISR[4] (if enabled via IER[5]) and causes IRCE#to go

LOW.

To resume transmission, an Xon1/Xon2 character must be received (in certain cases Xon1 and Xon2 must be received sequentially).

When the correct Xon characters are received, ISR[4] is cleared, and the Xoff interrupt disappears.

3.2 Transmit Flow Control

Xoff1/Xoff2 character is transmitted after the receive FIFO crosses the programmed halting level in TCR[3:0](if non-zero) or pro-

grammed receiver trigger level (for all trigger tables A-D). Xon1/Xon2 character is transmitted as soon as receive FIFO is below the

programmed resuming level in TCR[7:4](if non-zero) or less than one trigger level below the programmed receiver trigger level (for

Trigger Tables A, B, and C) or when receive FIFO is less than the trigger level minus the hysteresis value (for Trigger Table D). This

hysteresis value is the same as the Auto RTS Hysteresis value in Table 3.

Table 3. Selectable Hysteresis Levels When Trigger Table-D is Selected

FCTR BIT-3

FCTR BIT-2

FCTR BIT-1

FCTR BIT-0

RTS Hysteresis

(Characters)

0

0

0

0

0

0

0

0

1

+/- 4

0

0

1

0

+/- 6

0

0

1

1

+/- 8

0

1

0

0

+/- 8

0

1

0

1

+/- 16

0

1

1

0

+/- 24

0

1

1

1

+/- 32

1

1

0

0

+/- 12

1

1

0

1

+/- 20

1

1

1

0

+/- 28

1

1

1

1

+/- 36

1

0

0

0

+/- 40

1

0

0

1

+/- 44

1

0

1

0

+/- 48

1

0

1

1

+/- 52