XR17D154IV Exar Corporation, XR17D154IV Datasheet - Page 15

• Manufacturer Part Number: XR17D154IV
• Description: Universal QUART W/ PCI Bus Interface.
• Manufacturer: Exar Corporation

Specifications of XR17D154IV

• Features: *
• Number Of Channels: 4, QUART
• Fifo's: 64 Byte
• Protocol: RS485
• Voltage - Supply: 3.3V, 5V
• With Auto Flow Control: Yes
• With Irda Encoder/decoder: Yes
• With False Start Bit Detection: Yes
• With Modem Control: Yes
• Mounting Type: Surface Mount
• Package / Case: 144-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS Compliant

xr
XR17D154
UNIVERSAL (3.3V AND 5V) PCI BUS QUAD UART
REV. 1.2.2
2.2.1
The Interrupt Status Register
The XR17D154 has a 32-bit wide register [INT0, INT1, INT2 and INT3] to provide interrupt information and
supports two interrupt schemes. The first scheme uses bits 0 to 3 of an 8-bit indicator (INT0) representing
channels 0 to 3 of the XR17D154, respectively. 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 4
respectively, bits 4 to 7 are reserved and remain 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 and INT2 registers provide the 12-bit interrupt status
for all 4 channels. Bits 8, 9 and 10 representing channel 0 and bits 17,18 and 19 representing channel 3
respectively. Bits 20 to 31 are reserved and remain at logic zero. 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.
Figure 6
shows the 4-byte interrupt
register and its make up.
GLOBAL INTERRUPT REGISTER (DWORD) - [default 0x00-00-00-00]
INT3 [31:24]
INT2 [23:16]
INT1 [15:8]
INT0 [7:0]
A special interrupt condition is generated by the 154 when it wakes up from sleep mode. This special interrupt
is cleared by reading the INT0 register. If there are not any other interrupts pending, the value read from INT0
would be 0x00.
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 1 indicates that a channel has called for service. Bits 4 to 7 are reserved and remain
at logic 0 The interrupt bit clears after reading the appropriate register of the interrupting channel register, see
Interrupt Clearing section.
INT0 register provides status for each channel
INT0 Register
Individual UART Channel Interrupt Status
Rsvd
Rsvd Rsvd 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
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