xr17c152im Exar Corporation, xr17c152im Datasheet - Page 45

• Manufacturer Part Number: xr17c152im
• Description: 5v Pci Bus Dual Uart
• Manufacturer: Exar Corporation

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REV. 1.2.0
Enhanced features are enabled or disabled using this register. Bits 0-3 provide single or dual consecutive
character software flow control selection (see
are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that
whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before
programming a new setting.
EFR[3:0]: Software Flow Control Select
Combinations of software flow control can be selected by programming these bits. See
selections. The XOFF1/XOFF2 characters are transmitted approximately 2 character times after the RX FIFO
level has reached the RX trigger level, irrespective of which trigger table is used (Trigger Tables A-D). The
XON1/XON2 characters are transmitted when the RX FIFO level falls below the next lower trigger level for
Trigger Tables A-C and they are transmitted when the RX FIFO level falls below the (RX trigger level -
hysteresis level) for Trigger Table D. For example, if Trigger Table D is used with an RX trigger level of 56 and
a hysteresis level of 16, the XON1/XON2 characters are sent when the RX FIFO level count falls below 40.
4.8.14
Enhanced Feature Register (EFR) - Read/Write
T
ABLE
FCTR B
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
17: 16 S
IT
-3
FCTR B
ELECTABLE
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
IT
-2
H
FCTR B
YSTERESIS
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Table
IT
-1
18). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes
L
EVELS
45
FCTR B
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
W
IT
HEN
-0
T
RIGGER
RTS/DTR H
(
T
CHARACTERS
ABLE
± 16
± 24
± 32
± 12
± 20
± 28
± 36
± 40
± 44
± 48
± 52
± 4
± 6
± 8
± 8
0
-D
YSTERESIS
5V PCI BUS DUAL UART
IS
S
)
ELECTED
Table 18
for complete
XR17C152