xr17v254 Exar Corporation, xr17v254 Datasheet - Page 25

• Manufacturer Part Number: xr17v254
• Description: 66mhz Pci Bus Quad Uart With Power Management Support
• Manufacturer: Exar Corporation

REV. 1.0.0
MPIO3T [7:0] (default 0x00)
Output pin tri-state control. A logic 0 (default) sets the output to active level per register MPIOBIT settling, a
logic 1 sets the output pin to tri-state.
MPIOINV [7:0] (default 0x00)
Input inversion control. A logic 0 (default) does not invert the input pin logic. A logic 1 inverts the input logic
level.
MPIOSEL [7:0] (default 0xFF)
Multipurpose input/output pin select. This register defines the functions of the pins. A logic 1 (default) defines
the pin for input and a logic 0 for output.
The V254 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 4 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
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
2.0 CRYSTAL OSCILLATOR / BUFFER
). Alternatively, an external clock can be connected to the XTAL1 pin to clock the internal 4 baud rate
MPIO7
66MHZ PCI BUS QUAD UART WITH POWER MANAGEMENT SUPPORT
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
MPIO7
Multipurpose Input Signal Inversion Enable
MPIO6
MPIO6
Multipurpose Input/Output Selection
MPIO6
Multipurpose Output Level Control
MPIO6
Multipurpose Output 3-state Enable
MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIO5 MPIO4 MPIO3 MPIO2 MPIO1 MPIO0
MPIOLVL Register
MPIOSEL Register
MPIOINV Register
MPIO3T Register
25
page 29
for programming details.
XR17V254