xr16c872iq Exar Corporation, xr16c872iq Datasheet - Page 10

• Manufacturer Part Number: xr16c872iq
• Description: Dual Uart With 1284 Parallel Port And Plug-and-play Controller
• Manufacturer: Exar Corporation

XR16C872
Manual Configuration Mode Interface
The 872 provides an input pin (MAN#) to bypass the auto configuration procedure. It changes address lines A12-
A15 to manual configuration inputs S1-S4 and LPT. These inputs can be designed with external jumpers to select
COM1-COM4 for the serial ports, and LPT1 or LPT2 for the 1284 printer port.
Manual configuration mode supports the standard PC COM and LPT port addresses and associated IRQ. However,
the address lines can be mapped to other memory space areas for embedded applications, more on this later. The
872 eliminates the external address decoding logic circuitry that is typically required.
The manual configuration is selected by making the MAN# pin logic 0 (GND). This changes five address lines to
become configuration inputs. The manual configuration is accomplished by decoding the PC ISA bus address bits,
A3 through A10 inside the 872 for chip select. These addresses select the UART for standard PC COM ports: COM-
1, COM-2, COM-3, COM-4 and LPT-1 and LPT-2. Five inputs (S1-S5) are generally externally jumper or wired to
logic 1 or logic 0 for the operating port. The configuration inputs are also associated with a given PC interrupt. The
mapping for the COM port 1-4 and their associated interrupt selections are listed in Table 1. Besides the COM port
addresses, the 872 also decodes two parallel or printer addresses.
The chip can be mapped into an embedded system memory space. Figure 4 shows an example of wiring S1-S5
for default port configuration with IRQA and IRQB for the 2 UARTs, and IRQC with DREQ, and DACK for the parallel
port. Address lines A3-A10 are connected to the embedded system address lines A8-A15 instead, mapping it to
address location 0x7F08-7F0F, 0x5F00-5F08, and 0x6F00-6F08 respectively. Application note #xxxx describes how
to design with manual configuration mode in more detail.
Rev. 1.00
x: don't care
MAN#
0
0
0
0
0
0
0
0
0
0
S1 S2 S3 S4 S5
0
1
0
1
x
x
x
x
x
x
Table 1, Manual Configuration Mode Internal Addess Decode
0
0
1
1
x
x
x
x
x
x
x
x
x
x
0
1
0
1
x
x
x
x
x
x
0
0
1
1
x
x
x
x
x
x
x
x
x
x
1
0
DISCONTINUED
2E8-2EF
3E8-3EF
2E8-2EF
3E8-3EF
3F8-3FF
2F8-2FF
3F8-3FF
2F8-2FF
378-37F
278-27F
A3-A9
10
COM Port
COM-1
COM-2
COM-3
COM-4
COM-1
COM-2
COM-3
COM-4
LPT-1
LPT-2
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IRQ4
IRQ3
IRQ4
IRQ3
IRQ4
IRQ3
IRQ4
IRQ3
IRQ7
IRQ5
IRQ
Device Selected
UART Channel A
UART Channel A
UART Channel A
UART Channel A
UART Channel B
UART Channel B
UART Channel B
UART Channel B
1284 Parallel Port
1284 Parallel Port