xr16v2751im Exar Corporation, xr16v2751im Datasheet - Page 34

• Manufacturer Part Number: xr16v2751im
• Description: High Performance Duart With 64-byte Fifo And Powersave Feature
• Manufacturer: Exar Corporation

XR16V2751
HIGH PERFORMANCE DUART WITH 64-BYTE FIFO AND POWERSAVE FEATURE
EMSR[1:0]: Receive/Transmit FIFO Level Count (Write-Only)
When Scratchpad Swap (FCTR[6]) is asserted, EMSR bits 1-0 controls what mode the FIFO Level Counter is
operating in.
During Alternate RX/TX FIFO Level Counter Mode, the first value read after EMSR bits 1-0 have been
asserted will always be the RX FIFO Level Counter. The second value read will correspond with the TX FIFO
Level Counter. The next value will be the RX FIFO Level Counter again, then the TX FIFO Level Counter and
so on and so forth.
EMSR[2]: Reserved
EMSR[3]: Automatic RS485 Half-Duplex Control Output Inversion
•
•
EMSR[5:4]: Extended RTS Hysteresis
Logic 0 = RTS# output is LOW during TX and HIGH during RX (default, compatible with 16C2850).
Logic 1 = RTS# output is HIGH during TX and LOW during RX.
FCTR[6] EMSR[1] EMSR[0] Scratchpad is
0
1
1
1
EMSR
B
IT
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
X
X
0
1
-5
T
ABLE
T
ABLE
EMSR
B
13: S
IT
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
X
0
1
1
-4
14: A
CRATCHPAD
Scratchpad
RX FIFO Level Counter Mode
TX FIFO Level Counter Mode
Alternate RX/TX FIFO Counter Mode
FCTR
B
UTO
IT
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
-1
34
RTS H
S
FCTR
B
WAP
IT
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
YSTERESIS
-0
S
ELECTION
(C
H
HARACTERS
YSTERESIS
RTS#
±16
±24
±32
±40
±44
±48
±52
±12
±20
±28
±36
±4
±6
±8
±8
0
)
REV. 1.0.1