SC16C754 Philips Semiconductors, SC16C754 Datasheet - Page 12

• Manufacturer Part Number: SC16C754
• Description: Quad UART with 64-byte FIFO
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 11618
Product data
6.3.3 Software flow control example
6.4 Reset
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
60 characters have been sent. At this time, UART2 will transmit a 0F to UART1,
informing UART1 to halt transmission. UART1 will likely send the 61
UART2 is sending the Xoff character. Now UART2 is serviced and the processor
reads enough data out of the RX FIFO that the level drops to 32. UART2 will now
send a 0D to UART1, informing UART1 to resume transmission.
Table 4
Fig 7. Software flow control example.
summarizes the state of register after reset.
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 — 19 June 2003
Figure 7
shows an example of software flow control.
PROGRAMMED
CHARACTERS
Xoff–Xon–Xoff
COMPARE
Xon-Xoff
DATA
Quad 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
UART2
SC16C754
st
character while
002aaa229
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