Battery-backed clock, Serial ports, Battery-backed clock –12 serial ports –12 – Ampro Corporation LITTLE BOARD 5001451A User Manual

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2-12

Table 2-8. DMA Channel Assignments

Channel

Function

Available for 8-bit transfers

Floppy controller

Available for 8-bit transfers

Cascade for channels 0-3

Available for 16-bit transfers

Battery-Backed Clock

An AT-compatible battery-backed real-time clock (with CMOS RAM) is standard on the Little Board
P6d module. 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 the
board will function if the battery fails.

Note

The real-time clock date and time will not be correct without a
battery, or after the battery fails.

Serial Ports

The Little Board P6d module provides four RS232C serial ports, Serial 1 and Serial 2 at J8, and
Serial 3 and Serial 4 at J11.

Serial 1 and Serial 2 have full modem support. Serial 3 and Serial 4 support only RXD, TXD, RTS,
CTS. All ports support software selectable standard baud rates up to 115.2Kbps, 5-8 data bits, and
1, 1.5, or 2 stop bits.

Note

The IEEE RS232C specification limits the serial port to 19.2Kbps on
cables up to 50 feet in length.