Ampro Corporation P5X Battery-Backed Clock, Serial Ports, Addresses and Interrupt Assignments

Little Board/P5x Technical Manual

Battery-Backed Clock

An AT-compatible battery-backed real-time clock (with CMOS RAM) is standard on the Little Board/P5x. A 3.0 volt Lithium battery soldered to the board powers the clock. Battery drain for the clock is less than 0.4 uA. This battery will support the clock for more than 10 years of normal usage.

The factory initializes the real-time clock and various parameters in the configuration memory for a standard configuration. The factory sets the date and time, but it may not be set for your time zone. Use Setup to change these values as needed.

The contents of the configuration memory are also stored in an on-board EEPROM. The ROM BIOS reads the EEPROM to get configuration information if the CMOS RAM data is lost. This means that the board will function if the battery fails. Note that without a battery, the real-time clock date and time will not be correct.

Serial Ports

The Little Board/P5x provides four standard RS-232C serial ports, Serial 1 and Serial 2 at J11, and Serial 3 and Serial 4 at J13.

All ports support software selectable standard baud rates up to 115.2K bits/second, 5-8 data bits, and 1, 1.5, or 2 stop bits. Note that the IEEE RS-232C specification limits the serial port to 19.2K bits/second on cables up to 50 feet in length.

I/O Addresses and Interrupt Assignments

The serial ports appear at the standard port addresses as shown in Table 2– 10. Each serial port can be independently disabled using the Setup function, freeing its I/O addresses for use by other devices installed on the PC/104 and PCI expansion buses.

Table 2– 10 also shows the IRQs assigned to each serial port. Note that these interrupts are shared resources via serial interrupt protocol. (They do not have PC/104-type interrupt sharing circuits, as defined in the PC/104 specification.)

Table 2– 10. Serial Port I/O Addresses and Interrupts

Port	I/O Address	Interrupt
Serial 1	3F8h - 3FFh	4
Serial 2	2F8h - 2FFh	3
Serial 3	3E8h - 3EFh	3, 4, 5, 7, 9,
		10, 11, 12
Serial 4	2E8h - 2EFh	3, 4, 5, 7, 9,
		10, 11, 12

When a serial port is disabled, its I/O addresses and IRQ are available to other peripherals installed on the PC/104 expansion bus. You can disable any of the serial ports using Setup.

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