xr16l2750im Exar Corporation, xr16l2750im Datasheet - Page 31

• Manufacturer Part Number: xr16l2750im
• Description: High-performance 2.25v - 5.5v Duart
• Manufacturer: Exar Corporation

xr
REV. 1.2.1
MSR[3]: Delta CD# Input Flag
•
•
MSR[4]: CTS Input Status
CTS# pin may function as automatic hardware flow control signal input if it is enabled and selected by Auto
CTS (EFR bit-7). Auto CTS flow control allows starting and stopping of local data transmissions based on the
modem CTS# signal. A HIGH on the CTS# pin will stop UART transmitter as soon as the current character has
finished transmission, and a LOW will resume data transmission. Normally MSR bit-4 bit is the compliment of
the CTS# input. However in the loopback mode, this bit is equivalent to the RTS# bit in the MCR register. The
CTS# input may be used as a general purpose input when the modem interface is not used.
MSR[5]: DSR Input Status
Normally this bit is the complement of the DSR# input. In the loopback mode, this bit is equivalent to the DTR#
bit in the MCR register. The DSR# input may be used as a general purpose input when the modem interface is
not used.
MSR[6]: RI Input Status
Normally this bit is the complement of the RI# input. In the loopback mode this bit is equivalent to bit-2 in the
MCR register. The RI# input may be used as a general purpose input when the modem interface is not used.
MSR[7]: CD Input Status
Normally this bit is the complement of the CD# input. In the loopback mode this bit is equivalent to bit-3 in the
MCR register. The CD# input may be used as a general purpose input when the modem interface is not used.
This is a 8-bit general purpose register for the user to store temporary data. The content of this register is
preserved during sleep mode but becomes 0xFF (default) after a reset or a power off-on cycle.
This register replaces SPR (during a Write) and is accessible only when FCTR[6] = 1.
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
•
•
4.10
4.11
Logic 0 = No change on CD# input (default).
Logic 1 = Indicates that the CD# input has changed state since the last time it was monitored. A modem
status interrupt will be generated if MSR interrupt is enabled (IER bit-3).
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.
Scratch Pad Register (SPR) - Read/Write
Enhanced Mode Select Register (EMSR)
FCTR[6]
0
1
1
1
EMSR[1] EMSR[0]
X
X
0
1
T
ABLE
12: S
X
0
1
1
CRATCHPAD
Scratchpad
RX FIFO Level Counter Mode
TX FIFO Level Counter Mode
Alternate RX/TX FIFO Counter Mode
31
S
WAP
S
2.25V TO 5.5V DUART WITH 64-BYTE FIFO
S
CRATCHPAD IS
ELECTION
XR16L2750