xr16m2550 Exar Corporation, xr16m2550 Datasheet - Page 32

• Manufacturer Part Number: xr16m2550
• Description: High Performance Low Voltage Duart With 16-byte Fifo
• Manufacturer: Exar Corporation

XR16M2550
HIGH PERFORMANCE LOW VOLTAGE DUART WITH 16-BYTE FIFO
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 complement 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.
These registers make-up the value of the baud rate divisor. The concatenation of the contents of DLM and DLL
is a 16-bit value. Then the value is added to DLD[3:0]/16 to achieve the fractional baud rate divisor. DLD must
be enabled via EFR bit-4 before it can be accessed. See
Baud Rate Generator with Fractional Divisor” on page
DLD[5:4]: Sampling Rate Select
These bits select the data sampling rate. By default, the data sampling rate is 16X. The maximum data rate will
double if the 8X mode is selected and will quadruple if the 4X mode is selected. See
This register contains the device ID (0x02 for XR16M2550). Prior to reading this register, DLL and DLM should
be set to 0x00 (DLD = 0xXX).
4.10
4.11
4.12
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).
Scratch Pad Register (SPR) - Read/Write
Baud Rate Generator Registers (DLL, DLM and DLD) - Read/Write
Device Identification Register (DVID) - Read Only
DLD[5]
0
0
1
T
ABLE
13: S
AMPLING
DLD[4]
32
X
0
1
10.
Table 13
R
ATE
S
ELECT
below and
“Section 2.9, Programmable
S
AMPLING
Table 13
16X
8X
4X
R
ATE
below.
REV. 1.0.2