sc68c752b NXP Semiconductors, sc68c752b Datasheet - Page 10

• 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
Fig 6. CTS functional timing
(1) When CTS is LOW, the transmitter keeps sending serial data out.
(2) When CTS goes HIGH before the middle of the last stop bit of the current byte, the transmitter finishes sending the current
(3) When CTS goes from HIGH to LOW, the transmitter begins sending data again.
byte, but is does not send the next byte.
6.2.2 Auto-CTS
CTS
TX
6.3 Software flow control
The transmitter circuitry checks CTS before sending the next data byte. When CTS is
active, the transmitter sends the next byte. To stop the transmitter from sending the
following byte, CTS must be de-asserted before the middle of the last stop bit that is
currently being sent. The Auto-CTS function reduces interrupts to the host system. When
flow control is enabled, CTS level changes do not trigger host interrupts because the
device automatically controls its own transmitter. Without Auto-CTS, the transmitter sends
any data present in the transmit FIFO and a receiver overrun error may result.
Software flow control is enabled through the Enhanced Feature Register and the Modem
Control Register. Different combinations of software flow control can be enabled by setting
different combinations of EFR[3:0].
Table 4:
EFR[3]
0
1
0
1
X
X
X
1
0
1
Start
EFR[2]
0
0
1
1
X
X
X
0
1
1
Software flow control options (EFR[0:3])
byte 0 to 7
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
EFR[1]
X
X
X
X
0
1
0
1
1
1
Rev. 03 — 29 November 2005
Stop
EFR[0]
X
X
X
X
0
0
1
1
1
1
Table 4
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 compared Xon1, Xoff1
receiver compares Xon2, Xoff2
transmit Xon1, Xoff1
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
transmit Xon2, Xoff2
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
transmit Xon1, Xon2, Xoff1, Xoff2
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
shows software flow control options.
Start
byte 0 to 7
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
SC68C752B
002aaa227
Stop
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