Specifications
Hardware Configuration
2–47
2.15.2 Speaker Connections
The board supplies about 100 mW for a speaker on J16-7. Connect the other side of the speaker to
ground (J16-8). A transistor amplifier buffers the speaker signal. Use a small general purpose 2 or 3 inch
permanent magnet speaker with an 8 ohm voice coil. Refer to Chapter 3, Section 3.14 for an explanation
of the PC speaker circuit architecture.
2.15.3 Push-button Reset Connection
J16-9 provides a connection for an external normally-open momentary switch to manually reset the
system. Connect the other side of the switch to ground. The reset signal is “de-bounced” on the board.
2.15.4 Security Switch Connection
Connect a security switch between J16-10 and ground. The security switch can be a key switch (as
provided on desktop PCs) or other mechanical switch, or a digital signal that you provide. The security
switch locks out keyboard entry.
2.15.5 Keyboard Connection
You can connect an AT (not PC) keyboard to the keyboard port. J16-11 through J16-14 provide this
function. Normally, AT keyboards include a cable that terminates in a male 5-pin DIN plug for
connection to an AT (or a 6-pin miniature DIN plug for PS-2). Table 2–38 gives the keyboard connector
pinout and signal definitions, and includes corresponding pin numbers for DIN keyboard connectors.
Table 2–38 Keyboard Connector (J16)
J16 Pin Signal Name DIN-5
Pins
DIN-6
Pins
12 Keyboard Clock 1 5
11 Keyboard Data 2 1
13 Ground 4 3
14 Keyboard power 5 4
2.15.6 External Battery Connections
To connect an external battery to back up an SRAM in the byte-wide socket, connect its positive terminal
to J16-15 and its negative terminal to J16-16. Use a 3.6 volt lithium cell.
2.16 PC/104-PLUS EXPANSION BUS
The PC/104-Plus expansion bus appears on three header connectors, P1, P2, and J21. P1 is a 64-pin
female dual-row header. P2 is a 40-pin female dual-row header, and J21 is a 120-pin 2mm female quad-
row header (4 x 30). The PC-bus subset of the PC/104-Plus expansion bus connects to P1. The AT
expansion bus signals connect to P2. The layout of signals on P1 and P2 is compliant with the PC/104
bus specification, and make up the ISA bus portion of the PC/104-Plus bus. An implementation of the
PCI bus appears on J21.