XR17V258_08 Datasheet, PDF (27/70 Pages) Exar Corporation – 66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT

REV. 1.0.1
XR17V258
66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT
MPIOLVL Register
Multipurpose Output Level Control
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7 MPIO6 MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIO3T [7:0] (default 0x00)
The MPIO outputs can be tri-stated by the MPIO3T register. A logic 0 (default) sets the output to active level
per register MPIOBIT settling, a logic 1 sets the output pin to tri-state.
MPIO3T Register
Multipurpose Output 3-state Enable
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7 MPIO6 MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIOINV [7:0] (default 0x00)
The MPIO inputs can be inverted by the MPIOINV register. A logic 0 (default) does not invert the input pin logic.
A logic 1 inverts the input logic level.
MPIOINV Register
Multipurpose Input Signal Inversion Enable
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7 MPIO6 MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIOSEL [7:0] (default 0xFF)
The MPIOSEL register defines the MPIOs as either an input or output. A logic 1 (default) defines the pin for
input and a logic 0 for output.
MPIOSEL Register
Multipurpose Input/Output Selection
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7 MPIO6 MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
2.0 CRYSTAL OSCILLATOR / BUFFER
The V258 includes an on-chip oscillator (XTAL1 and XTAL2). The crystal oscillator provides the system clock
to the Baud Rate Generators (BRG) in each of the 8 UARTs, the 16-bit general purpose timer/counter and
internal logics. XTAL1 is the input to the oscillator or external clock buffer input with XTAL2 pin being the
output. See the Programmable Baud Rate Generator in the UART section on page 31 for programming details.
The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant with
10-22 pF capacitance load, 100ppm) connected externally between the XTAL1 and XTAL2 pins (see
Figure 10). Alternatively, an external clock can be connected to the XTAL1 pin to clock the internal 8 baud rate
27