XR17V254
16
66MHZ PCI BUS QUAD UART WITH POWER MANAGEMENT SUPPORT
REV. 1.0.1
1.6.1
The Global Interrupt Register
The XR17V254 has a 32-bit wide register [INT0, INT1, INT2 and INT3] to provide interrupt information and
supports two interrupt schemes. The first scheme is an 8-bit indicator representing all 4 channels with each bit
representing each channel from 0 to 3. This permits the interrupt routine to quickly vector and serve that UART
channel and determine the source(s) in each individual routines. INT0 bit [0] represents the interrupt status for
UART channel 0 when its transmitter, receiver, line status, or modem port status requires service. Other bits in
the INT0 register provide indication for the other channels with bit [3] representing UART channel 3
respectively. Bits 4 to 7 are reserved and remains at logic zero.
The second scheme provides detail about the source of the interrupts for each UART channel. All the interrupts
are encoded into a 3-bit code. This 3-bit code represents 7 interrupts corresponding to individual UART’s
transmitter, receiver, line status, modem port status. INT1, INT2 and INT3 registers provide the 24-bit interrupt
status for all 4 channels. Bits [10:8] representing channel 0 and bits [19:17] representing channel 3
respectively. Bits [31:20] are reserved. All 4 channel interrupts status are available with a single DWORD read
operation. This feature allows the host quickly vectors and serves the interrupts, reducing service interval,
hence, reduce host bandwidth requirement.
All bits start up zero. A special interrupt condition is generated by the V254 upon awakening from sleep after all
four channels were put to sleep mode earlier. This wake-up interrupt is cleared by a read to the INT0 register.
shows the 4-byte interrupt register and its make up.
INT0 [7:0] Channel Interrupt Indicator
Each bit gives an indication of the channel that has requested for service. Bit [0] represents channel 0 and
bit [3] indicates channel 3. Logic one indicates the channel N [3:0] has called for service. The interrupt bit
clears after reading the appropriate register of the interrupting channel register, see Interrupt Clearing section.
TABLE 7: DEVICE CONFIGURATION REGISTERS SHOWN IN DWORD ALIGNMENT
ADDRESS
REGISTER
BYTE 3 [31:24]
BYTE 2 [23:16]
BYTE 1 [15:8]
BYTE 0 [7:0]
0x080
-083
INTERRUPT (read-only)
INT3
INT2[
INT1
INT0
0x084-087
TIMER (read/write)
TIMERMSB
TIMERLSB
TIMER (reserved)
TIMERCNTL
0x088-08B
ANCILLARY1 (read/write)
SLEEP
RESET
REGA
8XMODE
0x08C-08F
ANCILLARY2 (read-only)
MPIOINT
REGB
DVID
DREV
0x090-093
MPIO (read/write)
MPIOSEL
MPIOINV
MPIO3T
MPIOLVL
GLOBAL INTERRUPT REGISTER (DWORD)
[default 0x00-00-00-00]
INT3 [31:24]
INT2 [23:16]
INT1 [15:8]
INT0 [7:0]
The INT0 register provides individual status for each channel
INT0 Register
Individual UART Channel Interrupt Status
Rsvd
Ch-3
Ch-2
Ch-1
Ch-0
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0