XR17C154 Datasheet, PDF (7/62 Pages) Exar Corporation – 5V PCI BUS QUAD UART

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REV. 1.3.0
XR17C154
5V PCI BUS QUAD UART
1.0 XR17C154 REGISTERS
The XR17C154 UART has three different sets of registers as shown in Figure 3. The PCI local bus configura-
tion space registers are for plug-and-play auto-configuration when connecting the device to the PCI bus. This
auto-configuration feature makes installation very easy into a PCI system and it is part of the PCI local bus
specification. The second register set is the device configuration registers that are accessible directly from the
PCI bus for programming general operating conditions of the device and monitoring the status of various func-
tions. These registers are mapped into 2K of the PCI bus memory address space. These functions include all 4
channel UART’s interrupt control and status, 16-bit general purpose timer control and status, multipurpose in-
puts/outputs control and status, sleep mode, soft-reset, and device identification and revision. And lastly, each
UART channel has its own set of 5G internal UART configuration registers for its own operation control and
status reporting. All 4 sets of channel registers are embedded inside the device configuration registers space,
which provides faster access. The following paragraphs describe all 3 sets of registers in detail.
FIGURE 3. THE XR17C154 REGISTER SETS
Device Configuration and
UART[3:0] Configuration
Registers are mapped on
to the Base Address
Register (BAR) in a 2K-
byte of memory address
space
PCI Local Bus
Target
Interface
PCI Local Bus
Configuration Space
Registers for Plug-
and-Play Auto
Configuration
Vendor and Sub-vendor ID
and Product Model Number
in External EEPROM
Channel 0
INT, MPIO,
TIMER, REG
Channel 0
Channel 1
Channel 2
Channel 3
0x0000
0x0080
0x0100
0x0200
0x0400
0x0600
0x07FF
Device Configuration Registers
4 channel Interrupts,
Multipurpose I/Os,
16-bit Timer/Counter,
Sleep, Reset, DVID, DREV
UART[3:0] Configuration
Registers
16550 Compatible and EXAR
Enhanced Registers
PCIREGS-1
1.1 PCI LOCAL BUS CONFIGURATION SPACE REGISTERS
The PCI local bus configuration space registers are responsible for setting up the device’s operating environ-
ment in the PCI local bus. The pre-defined operating parameters of the device are read by the PCI bus plug-
and-play auto-configuration manager in the operating system. After the PCI bus has collected all data from ev-
ery device/card on the bus, it defines and downloads the memory mapping information to each device/card
about their individual operation memory address location and conditions. The operating memory mapped ad-
dress location is downloaded into the Base Address Register (BAR) register, 0x10. The plug-and-play auto
configuration feature is only available when an external 93C46 EEPROM is used. The EEPROM contains the
device vendor and sub-vendor data required by the auto-configuration setup.
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