xr16m680 Exar Corporation, xr16m680 Datasheet - Page 11

• Manufacturer Part Number: xr16m680
• Description: 1.62v To 3.63v High Performance Uart With 32-byte Fifo
• Manufacturer: Exar Corporation

REV. 1.0.0
The RESET input resets the internal registers and the serial interface outputs to their default state (see
Table
the device. Following a power-on reset or an external reset, the M680 is software compatible with previous
generation of UARTs, XR16L580 and ST16C550.
The M680 has a set of 16550 compatible registers for controlling, monitoring and data loading and unloading.
These registers function as data holding registers (THR/RHR), interrupt status and control registers (ISR/IER),
a FIFO control register (FCR), receive line status and control registers (LSR/LCR), modem status and control
registers (MSR/MCR), programmable data rate (clock) divisor registers (DLL/DLM/DLD), and a user accessible
scratchpad register (SPR).
Beyond the general 16C550 features and capabilities, the M680 offers enhanced feature registers (EFR, Xon1/
Xoff 1, Xon2/Xoff 2, DLD, FCTR, EMSR and FC) that provide automatic RTS and CTS hardware flow control,
automatic Xon/Xoff software flow control, 9-bit (Multidrop) mode, auto RS-485 half duplex control, different
baud rate for TX and RX and fractional baud rate generator. All the register functions are discussed in full
detail later in
The interrupt outputs change according to the operating mode and enhanced features setup.
summarize the operating behavior for the transmitter and receiver. Also see
N
2.3
2.4
2.5
OTE
(16/68# = 1)
(16/68# = 0)
(16/68# = 1)
(16/68# = 0)
IRQ# Pin
: The IRQ# pin requires a pull-up resistor for proper operation.
IRQ# Pin
INT Pin
INT Pin
16). An active high pulse of longer than 40 ns duration will be required to activate the reset function in
Device Reset
Internal Registers
INT Ouput
“Section 3.0, UART INTERNAL REGISTERS” on page
LOW = One byte in THR
HIGH = THR empty
HIGH = One byte in THR
LOW = THR empty
HIGH = One byte in RHR
LOW = RHR empty
LOW = One byte in RHR
HIGH = RHR empty
FCR B
FCR B
IT
IT
-0 = 0 (FIFO D
-0 = 0 (FIFO D
T
ABLE
T
ABLE
1: INT P
1.62V TO 3.63V HIGH PERFORMANCE UART WITH 32-BYTE FIFO
2: INT P
ISABLED
ISABLED
IN
IN
O
)
)
PERATION FOR
O
PERATION FOR
11
LOW = FIFO above trigger level
HIGH = FIFO below trigger level or FIFO empty
HIGH = FIFO above trigger level
LOW = FIFO below trigger level or FIFO empty
LOW = FIFO below trigger level
HIGH = FIFO above trigger level or RX Data Timeout
HIGH = FIFO below trigger level
LOW = FIFO above trigger level or RX Data Timeout
T
RANSMITTER
R
ECEIVER
FCR B
FCR B
25.
IT
IT
Figure 22
-0 = 1 (FIFO E
-0 = 1 (FIFO E
through 25.
NABLED
NABLED
XR16M680
Table 1 and 2
)
)