Quatech ES-100 user manual Examination of a serial port base address

Page 10

A serial port's address is a 16-bit quantity that is most often expressed

in four hexadecimal (base 16) digits. A hex digit can hold a value from 0 to 15 (decimal), and is made up of four binary bits given weights of eight, four, two, and one, hence the maximum value of 8+4+2+1 = 15.

A possible serial port address is 5240 hex. The example below shows how the hex digits are broken down into binary bits.

Binary bits

0

1

0

1

0

0

1

0

0

1

0

0

0

0

0

0

Bit weight

8

4

2

1

8

4

2

1

8

4

2

1

8

4

2

1

Sum of bits

0+4+0+1

0+0+2+0

0+4+0+0

0+0+0+0

Hex digits

 

5

 

 

 

 

2

 

 

4

 

 

 

 

0

 

These address bits are set by the switches.

All other bits are considered to be zero.

0 1 0 1 0 0 1 0 0 1 0 0 0 0 0 0

Figure 4 --- Examination of a serial port base address

 

 

Switch on

 

Switch off

 

 

bit = 0

 

bit = 1

 

 

 

 

 

 

 

 

Factory default setting ---

0300 hex

A5-A0 are zero for the base address. Position 5 of SW2 is not used.

Position 6 of SW2 is used to enable or disable the interrupt status register.

SW1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

2

3

4

5

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

0

0

0

0

0

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

Another Example ---

5AC0 hex

 

 

 

SW1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

2

3

4

5

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

4

0

1

8

0

 

 

 

 

 

5

 

 

 

 

 

 

 

 

SW2

 

 

ON

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

2

 

3

4

5

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

1

 

0

0

 

(no digits)

3

 

 

 

 

 

 

0

 

 

0

 

 

SW2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ON

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

2

 

3

4

5

6

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

0

 

8

4

 

(no digits)

A

 

 

 

 

C

 

 

0

 

 

Figure 5 --- Serial port base I/O address selection switches

Quatech ES-100D User's Manual

5

Image 10
Contents ES-100 Page Warranty Information Page EC Council Directive 89/336/EEC FCC Class BGeneral Information Installation Port Address IRQDiagram of ES-100D Setting the address Addressing PortsExamination of a serial port base address Interrupt Sharing Interrupt Level IRQInterrupt Status register Interrupt Status Register contents This page intentionally left blank External Connections Channel Output Configuration ES-100D connector definitionsES-100D output connectors Serial Port Functional Description Accessing the Serial Port registers DlabInterrupt Enable Register Interrupt Identification RegisterInterrupt Identification Register bit definitions Fifo Control Register 16550 only RXT0Line Control Register EPS PEN ParityModem Control Register Modem Control Register bit definitionsLine Status Register Line Status Register bit definitionsModem Status Register Scratchpad RegisterFifo Interrupt Mode Operation 16550 Uart only When the receiver Fifo and receiver interrupts are enabledFifo polled mode operation 16550 Uart only Baud Rate Selection Value Values %Specifications 16450 16550 optionalTroubleshooting Computer will not boot upVersion March Quatech Inc, ES-100 Manual