XR16L2552
31
REV. 1.1.2 2.25V TO 5.5V DUART WITH 16-BYTE FIFO
MSR[1]: Delta DSR# Input Flag
Logic 0 = No change on DSR# input (default).
Logic 1 = The DSR# 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).
MSR[2]: Delta RI# Input Flag
Logic 0 = No change on RI# input (default).
Logic 1 = The RI# input has changed from a logic 0 to a logic 1, ending of the ringing signal. A modem status
interrupt will be generated if MSR interrupt is enabled (IER bit-3).
MSR[3]: Delta CD# Input Flag
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).
MSR[4]: CTS Input Status
Normally this 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 compliment 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 compliment 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 compliment 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.
4.11 Scratch Pad Register (SPR) - Read/Write
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.
4.12 Baud Rate Generator Registers (DLL and DLM) - Read/Write
The concatenation of the contents of DLM and DLL gives the 16-bit divisor value which is used to calculate the
baud rate:
Baud Rate = (Clock Frequency / 16) / Divisor
See MCR bit-7 and the baud rate table also.
4.13 Alternate Function Register (AFR) - Read/Write
This register is used to select specific modes of MF# operation and to allow both UART register sets to be
written concurrently.
XR16L2552
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2.25V TO 5.5V DUART WITH 16-BYTE FIFO REV. 1.1.2
AFR[0]: Concurrent Write Mode
When this bit is set, the CPU can write concurrently to the same register in both UARTs. This function is
intended to reduce the dual UART initialization time. It can be used by the CPU when both channels are
initialized to the same state. The external CPU can set or clear this bit by accessing either register set. When
this bit is set, the channel select pin still selects the channel to be accessed during read operations. The user
should ensure that LCR Bit-7 of both channels are in the same state before executing a concurrent write to the
registers at address 0, 1, or 2.
Logic 0 = No concurrent write (default).
Logic 1 = Register set A and B are written concurrently with a single external CPU I/O write operation.
AFR[2:1]: MF# Output Select
These bits select a signal function for output on the MF# A/B pins. These signal function are described as:
OP2#, BAUDOUT#, or RXRDY#. Only one signal function can be selected at a time.
AFR[7:3]: Reserved
All are initialized to logic 0.
4.14 Device Identification Register (DVID) - Read Only
This register contains the device ID (0x02 for XR16L2552). Prior to reading this register, DLL and DLM should
be set to 0x00.
4.15 Device Revision Register (DREV) - Read Only
This register contains the device revision information. For example, 0x01 means revision A. Prior to reading
this register, DLL and DLM should be set to 0x00.
4.16 Enhanced Feature Register (EFR)
Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive
character software flow control selection (see Table 12). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes
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.
BIT-2 BIT-1 MF# FUNCTION
0 0 OP2# (default)
0 1 BAUDOUT#
1 0 RXRDY#
11 Reserved
XR16L2552
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REV. 1.1.2 2.25V TO 5.5V DUART WITH 16-BYTE FIFO
EFR[3:0]: Software Flow Control Select
Single character and dual sequential characters software flow control is supported. Combinations of software
flow control can be selected by programming these bits.
EFR[4]: Enhanced Function Bits Enable
Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, and MCR bits 5-7 to be modified.
After modifying any enhanced bits, EFR bit-4 can be set to a logic 0 to latch the new values. This feature
prevents legacy software from altering or overwriting the enhanced functions once set. Normally, it is
recommended to leave it enabled, logic 1.
Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, and MCR bits 5-7 are
saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, and MCR bits 5-7are set to a
logic 0 to be compatible with ST16C550 mode (default).
Logic 1 = Enables the above-mentioned register bits to be modified by the user.
EFR[5]: Special Character Detect Enable
Logic 0 = Special Character Detect Disabled (default).
Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with
data in Xoff-2 register. If a match exists, the receive data will be transferred to FIFO and ISR bit-4 will be set
to indicate detection of the special character. Bit-0 corresponds with the LSB bit of the receive character. If
flow control is set for comparing Xon1, Xoff1 (EFR [1:0]= ‘10’) then flow control and
special character work
normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]= ‘01’) then flow control works
normally, but Xoff2 will not
go to the FIFO, and will generate an Xoff interrupt and a special character
interrupt, if enabled via IER bit-5. Special character interrupts are cleared automatically after the next
received character.
T
ABLE 12: SOFTWARE FLOW CONTROL FUNCTIONS
EFR BIT-3
CONT-3
EFR BIT-2
CONT-2
EFR
BIT-1
C
ONT-1
EFR
BIT-0
C
ONT-0
T
RANSMIT AND RECEIVE SOFTWARE FLOW CONTROL
0 0 0 0 No TX and RX flow control (default and reset)
0 0 X X No transmit flow control
1 0 X X Transmit Xon1, Xoff1
0 1 X X Transmit Xon2, Xoff2
1 1 X X Transmit Xon1 and Xon2, Xoff1 and Xoff2
X X 0 0 No receive flow control
X X 1 0 Receiver compares Xon1, Xoff1
X X 0 1 Receiver compares Xon2, Xoff2
1 0 1 1 Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
0 1 1 1 Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
1 1 1 1 Transmit Xon1 and Xon2, Xoff1 and Xoff2,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
0 0 1 1 No transmit flow control,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2

XR16L2552IJTR-F

Mfr. #:
Manufacturer:
MaxLinear
Description:
UART Interface IC UART
Lifecycle:
New from this manufacturer.
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