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Philips Semiconductors
9397 750 11621
Product data
Dual UART with 16 bytes of transmit and receive FIFOs and IrDA
Table 20:
Enhanced Feature Register bits description
Bit
Symbol
Description
5
EFR[5]
Special Character Detect.
Logic 0 = Special character detect disabled (normal default condition).
Logic 1 = Special character detect enabled. The SC16C2550 compares
each incoming receive character with Xoff2 data. If a match exists, the
received data will be transferred to FIFO and ISR[4] will be set to
indicate detection of special character. Bit-0 in the X-registers
corresponds with the LSB bit for the receive character. When this feature
is enabled, the normal software flow control must be disabled (EFR[3-0]
must be set to a logic 0).
4
EFR[4]
Enhanced function control bit. The content of IER[7-4], ISR[5-4], FCR[5-4],
and MCR[7-5] can be modified and latched. After modifying any bits in the
enhanced registers, EFR[4] can be set to a logic 0 to latch the new values.
This feature prevents existing software from altering or overwriting the
SC16C2550 enhanced functions.
Logic 0 = disable/latch enhanced features. IER[7-4], ISR[5-4], FCR[5-4],
and MCR[7-5] are saved to retain the user settings, then IER[7-4]
ISR[5-4], FCR[5-4], and MCR[7-5] are set to a logic 0 to be compatible
with SC16C554 mode. (Normal default condition.)
Logic 1 = Enables the enhanced functions. When this bit is set to a
logic 1, all enhanced features of the SC16C2550 are enabled and user
settings stored during a reset will be restored.
3-0
EFR[3-0] Cont-3-0 Tx, Rx control. Logic 0 or cleared is the default condition.
Combinations of software flow control can be selected by programming
these bits. See
Table 21:
Software flow control functions
Cont-3
Cont-2
Cont-1
0
0
X
1
0
X
0
1
X
1
1
X
X
X
0
X
X
1
X
X
0
1
0
1
0
1
1
1
1
1
[1]
When using a software flow control the Xon/Xoff characters cannot be used for data transfer.
Rev. 03 — 19 June 2003
Table
21.
[1]
Cont-0
TX, RX software flow controls
X
No transmit flow control
X
Transmit Xon1/Xoff1
X
Transmit Xon2/Xoff2
X
Transmit Xon1 and Xon2/Xoff1 and Xoff2
0
No receive flow control
0
Receiver compares Xon1/Xoff1
1
Receiver compares Xon2/Xoff2
1
Transmit Xon1/Xoff1
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
1
Transmit Xon2/Xoff2
Receiver compares Xon1 and Xon2/Xoff1 and Xoff2
1
Transmit Xon1 and Xon2/Xoff1 and Xoff2
Receiver compares Xon1 and Xon2/Xoff1 and Xoff2
SC16C2550
encoder/decoder
...continued
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
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