TL16C752C Datasheet, PDF (9/50 Pages) Texas Instruments – DUAL UART WITH 64-BYTE FIFO

www.ti.com
BIT 3
0
1
0
1
X
X
X
1
0
1
0
TL16C752C
DUAL UART
WITH 64-BYTE FIFO
SLLS646 – MARCH 2008
Table 1. Software Flow Control Options EFR[3:0]
BIT 2
0
0
1
1
X
X
X
0
1
1
0
BIT 1
X
X
X
X
0
1
0
1
1
1
1
BIT 0
X
X
X
X
0
0
1
1
1
1
1
Tx, Rx SOFTWARE FLOW CONTROLS
No transmit flow control
Transmit Xon1, Xoff1
Transmit Xon2, Xoff2
Transmit Xon1, Xon2: Xoff1, Xoff2
No receive flow control
Receiver compares Xon1, Xoff1 X X 0 1
Receiver compares Xon2, Xoff2
Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon1, Xon2: Xoff1, Xoff2
Receiver compares Xon1 and Xon2: Xoff1 and Xoff2
No transmit flow control
Receiver compares Xon1 and Xon2: Xoff1 and Xoff2
When software flow control operation is enabled, the TL16C752C compares incoming data with Xoff1/2
programmed characters (in certain cases Xoff1 and Xoff2 must be received sequentially⁽¹⁾). When an Xoff
character is received, transmission is halted after completing transmission of the current character. Xoff character
detection also sets IIR[4] and causes INT to go high (if enabled via IER[5]).
To resume transmission an Xon1/2 character must be received (in certain cases Xon1 and Xon2 must be
received sequentially). When the correct Xon characters are received IIR[4] is cleared and the Xoff interrupt
disappears.
NOTE:
If a parity, framing or break error occurs while receiving a software flow control
character, this character is treated as normal data and is written to the RCV FIFO.
Xoff1/2 characters are transmitted when the RX FIFO has passed the programmed trigger level TCR[3:0].
Xon1/2 characters are transmitted when the RX FIFO reaches the trigger level programmed via TCR[7:4].
NOTE:
If, after an Xoff character has been sent, software flow control is disabled, the UART
transmits Xon characters automatically to enable normal transmission to proceed. A
feature of the TL16C752C UART design is that if the software flow combination
(EFR[3:0]) changes after an Xoff has been sent, the originally programmed Xon is
automatically sent. If the RX FIFO is still above the trigger level the newly
programmed Xoff1/2 is transmitted.
The transmission of Xoff/Xon(s) follows the exact same protocol as transmission of an ordinary byte from the
FIFO. This means that even if the word length is set to be 5, 6, or 7 characters, then the 5, 6, or 7 least
significant bits of Xoff1,2/Xon1,2 are transmitted. The transmission of 5, 6, or 7 bits of a character is seldom
done, but this functionality is included to maintain compatibility with earlier designs.
It is assumed that software flow control and hardware flow control are never enabled simultaneously. Figure 4
shows a software flow control example.
(1) When pairs of Xon/Xoff characters are programmed to occur sequentially, received Xon1/Xoff1 characters will be written to the Rx FIFO
if the subsequent character is not Xon2/Xoff2.
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TL16C752C
Submit Documentation Feedback
9