User manual

DIGITAL-LOGIC AG MSB900/L Detailed Technical Manual V1.0

5.4.3. Serial Ports COM1-COM2

The serial channels are fully compatible with 16C550 UARTS. COM1 is the primary serial port, and is sup-

ported by the board's ROM-BIOS as the PC-DOS 'COM1' device. The secondary serial port is COM2; it is

supported as the 'COM2' device.

Standard: COM 1/2: National PC87317VUL: 2 x 16C550 compatible serial interfaces

Serial Port Connectors COM1, COM2

Pin Signal Name Function in/out DB25 Pin

DB9 Pin

1 CD Data Carrier Detect in 8 1

2 DSR Data Set Ready in 6 6

3 RXD Receive Data in 3 2

4 RTS Request To Send out 4 7

5 TXD Transmit Data out 2 3

6 CTS Clear to Send in 5 8

7 DTR Data Terminal Ready out 20 4

8 RI Ring Indicator in 22 9

9 GND Signal Ground 7 5

The serial port signals are compatible with the RS232C specifications.

5.4.4. Floppy Disk Interface

This is not available with this product; use a USB Floppy.

5.5. Controllers

5.5.1. Interrupt Controllers

An 8259A compatible interrupt controller, within the chipset, provides seven prioritized interrupt levels. Of

these, several are normally associated with the board's onboard device interfaces and controllers, and sev-

eral are available on the AT expansion bus.

Interrupt: Sources: Onboard used:

IRQ0 ROM-BIOS clock tick function, from timer 0 yes

IRQ1 Keyboard controller output buffer full yes

IRQ2 Used for cascade 2. 8259 yes

IRQ3 COM2 serial port yes

IRQ4 COM1 serial port yes

IRQ5 LPT2 parallel printer (if present) no *

IRQ6 Floppy controller yes

IRQ7 LPT1 parallel printer yes

IRQ8 Battery backed clock yes

IRQ9 Free for user no *

IRQ10 Free for user no *

IRQ11 Free for user no *

IRQ12 PS/2 mouse yes

IRQ13 Math. coprocessor yes

IRQ14 Hard disk IDE yes

IRQ15 Free for user no *

* It may depend on the LAN configuration.