sc68c752b NXP Semiconductors, sc68c752b Datasheet - Page 12

• Manufacturer Part Number: sc68c752b
• Description: 5 V, 3.3 V And 2.5 V Dual Uart, 5 Mbit/s Max. , With 64-byte Fifos And Motorola Up Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
SC68C752B_3
Product data sheet
6.3.3.1 Assumptions
6.3.3 Software flow control example
UART1 is transmitting a large text file to UART2. Both UARTs are 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.
UART1 begins transmission and sends 52 characters, at which point UART2 will generate
an interrupt to its processor to service the RX 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 0Fh to UART1, informing UART1 to halt
transmission. UART1 will likely send the 61
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 0Dh to UART1, informing UART1
to resume transmission.
Fig 7. Software flow control example
SERIAL-TO-PARALLEL
PARALLEL-TO-SERIAL
TRANSMIT FIFO
Xon1 WORD
Xon2 WORD
Xoff1 WORD
Xoff2 WORD
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
UART1
Rev. 03 — 29 November 2005
Xoff–Xon–Xoff
programmed
characters
compare
Xon-Xoff
st
data
character while UART2 is sending the Xoff
SERIAL-TO-PARALLEL
PARALLEL-TO-SERIAL
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
RECEIVE FIFO
Xon2 WORD
Xon1 WORD
Xoff1 WORD
Xoff2 WORD
SC68C752B
UART2
002aaa229
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