B&B Electronics 3PXCC1b, 3PXCC1A, 3PXCC2b, 3PXCC2a manual Interrupt Jumper Setup

When setting the address (via the dipswitch) use the silkscreen on the printed circuit board. This silkscreen shows a “1” and a “0” to refer to the “on and “off” states that each switch is set to. Switch S1 configures port one (labeled J1) and, on two port cards, switch S2 configures port two (labeled J2). Least significant bit (LSB) and most significant bit (MSB) are labeled on the card. Table 1 shows the numerical weight and electrical connection of each switch position. Refer to Table 2 for COM port addresses. Table 3 shows frequently unused port addresses for applications when COM port addresses 1-4 are already used.

Table 1. Address Switches

Switch Position	7	6	5	4	3	2	1
Bus Connection	SA9	SA8	SA7	SA6	SA5	SA4	SA3
Decimal Weight	512	256	128	64	32	16	8
Hex Weight	200	100	80	40	20	10	8

To install the 3PXCC card as COM1, 2, 3, or 4, follow the switch settings shown in Table 2. To install at another address, follow the switch settings shown in Table 3.

Table 2. Standard Port Addresses

	Base Hex	Binary	Switch Settings
	Address	Equivalent	MSB LSB
			7654321
COM1	3F8	1111111000	1111111
COM2	2F8	1011111000	1011111
COM3	3E8	1111101000	1111101
COM4	2E8	1011101000	1011101

Documentation No.3PXCC1x-2x-3903 31

Table 3. Frequently Unused Port Addresses

Base	Binary	Switch	I/O Space
Hex	Equivalent	Settings	Description
Address		MSB LSB
		7654321
200	1000000000	1000000	game port
208	1000001000	1000001	game port
300	1100000000	1100000	prototype
308	1100001000	1100001	prototype
310	1100010000	1100010	prototype
318	1100011000	1100011	prototype
380	1110000000	1110000	SDLC
388	1110001000	1110001	SDLC
3A0	1110100000	1110100	bisync com
3A8	1110101000	1110101	bisync com

Interrupt Jumper Setup

The IRQ is a hardware Interrupt Request line in an ISA Bus expansion slot on a PC or AT compatible computer. The 8 bit PC ISA slot has 8 interrupts, the 16 bit slot has another 7 since one of the first 8 is used to link in the remaining 8. The IRQ is used by devices to request immediate service by the main microprocessor. When the IRQ line is set, the microprocessor stops whatever it’s doing, saves status, checks which line was set, then jumps to code to handle the interrupt. The processor then clears the interrupt and returns to what it was doing before. IRQ lines are set by the internal timer, keyboard, hard drive controller, PCI, USB controller, sound card, serial ports, printer and more. The 3PXCC2 serial cards include special circuitry which allows one IRQ to be shared between the cards two ports even during simultaneous use. The software driver must support shared IRQs for this feature to work. Both Windows 9x and NT support shared IRQs. To configure both ports of the card to share one IRQ, set both jumpers of JP4 to the “Share” position. The Port 1 IRQ Select jumper should then be set to the desired IRQ. The Port 2 IRQ Select jumper is ignored when in shared mode.

The 3PXCC cards allow the use of interrupts (IRQ) 2, 3, 4, 5, 6, 7, 10, 11, 12, 14, and 15. Table 4 shows the standard serial port IRQ settings. NOTE: If two ports use the same IRQ setting, both ports cannot use the serial port at once. Only one port at a time may communicate.

32 Documentation No.3PXCC1x-2x-3903

B&B Electronics Mfg Co – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104	B&B Electronics Mfg Co – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Comm. Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445	B&B Electronics Ltd – Westlink Comm. Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445