sc16c752 NXP Semiconductors, sc16c752 Datasheet - Page 10

• Manufacturer Part Number: sc16c752
• Description: Dual Uart With 64-byte Fifo
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 11635
Product data
6.3.2 TX
6.3.3 Software flow control example
Xoff1/2 character is transmitted when the RX FIFO has passed the HALT trigger level
programmed in TCR[3:0].
Xon1/2 character is transmitted when the RX FIFO reaches the RESUME trigger
level programmed in TCR[7:4].
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 will be
transmitted. (Note that 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 will never be
enabled simultaneously.
Assumptions:
using software flow control with single character Xoff (0F) and Xon (0D) tokens. Both
have Xoff threshold (TCR[3:0] = F) set to 60, and Xon threshold (TCR[7:4] = 8) set to
32. Both have the interrupt receive threshold (TLR[7:4] = D) set to 52.
UART 1 begins transmission and sends 52 characters, at which point UART2 will
generate an interrupt to its processor to service the RCV FIFO, but assume the
interrupt latency is fairly long. UART1 will continue sending characters until a total of
Fig 6. Software flow control example.
PARALLEL-TO-SERIAL
SERIAL-TO-PARALLEL
TRANSMIT FIFO
UART1 is transmitting a large text file to UART2. Both UARTs are
Xon-1 WORD
Xon-2 WORD
Xoff-1 WORD
Xoff-2 WORD
UART1
Rev. 04 — 20 June 2003
Figure 6
shows an example of software flow control.
PROGRAMMED
CHARACTERS
Xoff–Xon–Xoff
COMPARE
Xon-Xoff
DATA
Dual UART with 64-byte FIFO
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
SERIAL-TO-PARALLEL
PARALLEL-TO-SERIAL
RECEIVE FIFO
Xon-1 WORD
Xon-2 WORD
Xoff-1 WORD
Xoff-2 WORD
SC16C752
UART2
002aaa229
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