Technical Documentation
Simtec EB7500ATX Series Motherboards
Internal Pinout and Link Settings
Simtec Technical document EB7500ATX/2
Issue 2, February 2001
The information contained in this booklet is 2000 Simtec Electronics
This document must not be reproduced by any means by persons other than the copyright holders
Internal front panel connectors:
PL6
Speaker
Mono Speaker connector capable of driving 1.1W in an 8 Ohm load. Speaker volume can be set by adjusting the
trimmer R163. Anti-clockwise increases volume, clockwise decreases volume.
Pin
Function
1
speaker+
2
speaker-
3
speaker+
4
speaker-
PL24 IRDA - infra red serial port
Encoded IRDA serial connector
Pin
Function
Comment
1
Vcc
+5V supply
2
FIR
output (only with SMSC37C669FR fitted)
3
IRRX
input
4
GND
Ground
5
IRTX
output
6
XCVR/OFF
output
PL19 LED and LK - Power state LED and keyboard lock
Pins 1,2,3.
Front panel LED driven by power management controller. When the computer is in standby this LED will flash to
indicate that mains power is still connected. The exact rate and pattern of the flashes can be configured. When the unit
is on, the LED will be lit constantly.
Pins 4,5.
If a keyswitch is connected to these two pins, the Keyboard lock (LK) will completely disable both keyboard and mouse
inputs. When the keyswitch is closed input will be disabled. When open, or when no switch is fitted, keyboard and
mouse input will be enabled as normal.
Pin
Function
1
LED+
)
2
NC

) LED
3
LED-
)
4
Key Lock input ) LK
5
GND
)
Page 2
LK4
PWR - Soft Power on switch
When the computer is in "standby", a momentary closure on the power switch connected between these pins will turn on
the mains power. If it is pressed again, it will signal the computer to perform a system shutdown, turn off the power and
enter it's standby mode. If for some reason the system refuses to shut down automatically, holding the button
continuously for four seconds will force the power to be turned off.
Pin
Function
1
Power on switch
input
2
GND
LK3
HD - Hard disk and network activity LED
When a LED is connected to these pins, it will light when either on of the connected IDE devices is being accessed or
when a network packet addressed to the computer has been received.
Pin
Function
1
LED+
2
LED-
LK5
RST - System reset button
The system reset button should be connected to these pins. When pressed, it will force the machine to reset and all
data and programmes currently held in RAM will be lost. It should only be used on the rare occasions when the
computer ceases to respond and escape, <ALT><BREAK> or <CTRL><BREAK> don't work.
Pin
Function
1
Reset
input
2
GND
LK9
WAKE - Remote Wake-on-lan connector
This connector is used to power an expansion card when main power is off and the system is in standby mode. If
enabled in the power management setup, a positive going signal on the wake-up pin will power on the machine.
Pin
Function
1
+5V supply
2
GND
3
Wake-up
input
LK11 VARFAN - Programmable 12V FAN
This connector can be used to power a small 12V FAN that draws less than 250mA. The speed can be controlled by
software using the power monitor. The connector also has a TACHO input so that fans that support it can be monitored
to verify rotational speed or to detect a rotor stall.
Pin
Function
1
GND
2
+FAN supply (0-10V)
3
Open collector TACHO input
input/OC
Page 3
LK6
12V FAN - unfused 12V supply for additional FAN
Pin
Function
1
GND
2
+12V supply
3
NC
LK1,2,17,18
These are for manufacturing and test only and should not be altered. Do not fit any jumper caps to these pins.
PL22 System ID bits
These pins may be populated by link caps and their state can be read back by software. These pins are not currently
used. Fitting a link cap between a pair of pins will cause a logic zero to be read back for the corresponding bit position.
When no cap is fitted, a logic "1" is returned.
Pin
Function
1-2
VID0
3-4
VID1
5-6
VID2
7-8
VID3 - Keyboard Fuse blown
*DO NOT FIT LINK*
9-10
VID4 - Joystick Fuse blown
*DO NOT FIT LINK*
PL12 CMOS protect and ROM size select
This setting of the link caps between pins 1-2 and 3-4 set the size of each ROM bank. The RED cap on on pins 5-6 is
used to prevents CMOS RAM from being cleared by a holding <DELETE> or "R" on power on. When this link is
removed, the CMOS is protected.
Pin
Function
1-2
ROMSEL 0
3-4
ROMSEL 1
5-6

ROMSEL 3 - CMOS protection
The size and type of ROMs can be set according to the link table below:
ROMSEL 1
ROMSEL 0
Setting
Fitted
Fitted
Bank0=16Mb/Bank1=16Mb - Bank 0 used to boot processor
Fitted
NF
Bank1=16Mb/Bank0=16Mb - Bank 0 and 1 swapped
NF
Fitted
Bank0=32Mb/Bank1 disabled
NF
NF
Bank1=32Mb/Bank0 disabled
ROMSEL1 and ROMSEL2 should not need to be changed. The machine will not work correctly if they are
inappropriately set. *Default, all links are fitted.
Page 4
LK10 OWB - One wire bus/Dallas ID socket
This socket accepts a Dallas serial number device and can be used to replace the machine's default serial number.
Pin
Function
1
GND
2
One wire signal bus
in/out
3
+5V supply fed by
22 Ohm protection
resistor
LK7,13
SERIAL/MIDI - selects between Serial 2 and MIDI 2
These links route the second UART signals of the SuperIO device to either the second serial connector (PL21) for a
second serial port or to the second joystick port (PL2) for a second MIDI port.
By default, the signals are set for serial mode. The jumper cap positions for each mode for LK7 and LK13 are as follows:
Pin
Function
1-2, 1-2
SERIAL mode to second serial port
2-3, 2-3
MIDI mode to second midi port
PL4
AUX BAT/RAM CLR - CMOS RAM clear link and auxiliary battery connector
If enabled by software, the CMOS RAM may be cleared by moving the link cap from its parking position, pin 2-3 to
position 3-4 while power is on. The cap should then be returned to its parking position after the RAM has been reset.
The header also serves as a connector for an standard 4.5v auxiliary battery pack which can be used to maintain the
CMOS RAM and Realtime clock if the internal cell finally discharges after ten years of use. As replacing the RTC
module may stop some protected software from running if a specific machine serial number is expected, an external
battery should be used.
Pin
Function
1
+3.5-4.5v aux battery supply
2
NC
) Parking position for
3
CMOS RAM clear (in) ) RAM clear jumper cap
4
GND
Page 5
PL2
JOYSTICK - secondary joystick connector
This second joystick port is connected to the 7500FE's analogue inputs and is completely independent of the external
port. It can also provide an additional MIDI channel if LK7 and 13 are set appropriately.
Pin
Function
1
+5V supply
(250mA fused)
2
+5V supply
3
JAB1 - Joystick A, button 1
4
JBB1 - Joystick B, button 1
5
JACX - Joystick A, x-axis
6
JBCX - Joystick B, x-axis
7
GND
8
MIDI_TX - Midi out
9
GND
10
JBCY - Joystick B, y-axis
11
JACY - Joystick A, y-axis
12
JBB2 - Joystick B, button 2
13
JAB2 - Joystick A, button 2
14
MIDI_RX - Midi in
15
+5V supply
16
NC
PL9
IIC - IIC serial comminication bus
The IIC serial bus is a two wire synchronous serial bus devised by Philips Components as an efficient way to connect
multiple low speed devices to a CPU. RISC OS' IIC bus brought out to a four pin header, providing power, clock,
data and ground. Both clock and data signals have ESD clamp diodes to protect the inputs from excessive static
discharge. For information on how to use the IIC bus, read the RISC OS programmers ref. manuals and consult the
current IIC standard from Philips Semiconductors.
Pin
Function
1
+5V Supply
2
IIC Data
in/out
3
IIC Clock
in/out
4
GND
PL5
VOLUME - digital volume control
When a multimedia switch panel is connected to the digital volume port, the master volume of the sound system can be
increased, decreased or muted by pressing the appropriate button which connects it's signal to ground. Holding a
button down will continue to increase/decrease the volume until released or the maximum or minimum is reached.
Pin
Function
1
MUTE
2
UP
3
DOWN
4
GND
Page 6
PL8,11
CD AUDIO
These two connectors are wired together to enable the sound output of a CD drive to be mixed with the internal sound
so it can be fed through the speaker and LINE OUT. Two types are supported so that all common CD audio cables can
be used. Use the connector that matches the pitch and wiring of your CD's cable.
As both sockets are wired together, only one socket should be used at any one time. Do not connect a second drive
to the other socket or damage to the device will occur.
Use the separate AUX AUDIO connector PL7 for an
additional sound input (*SEE PL7 AUX AUDIO over restrictions if a wavetable card is fitted)
PL8
0.1 inch pitch CD audio connector
Pin
Function
1
Left Audio
2
GND
3
GND
4
Right Audio
PL11 2mm pitch CD audio connector
Pin
Function
1
Left Audio
2
GND
3
Right Audio
4
GND
PL14
WAVETABLE EXPANSION - Wavetable connector
PL7
AUX AUDIO - additional audio mixer input
PL13
DSP - serial audio DSP interface
This connector will take a standard MIDI synth board. If feeds both power and the MIDI-out stream to the synth and
routes its audio output through the sound mixer. If the wavetable connector is not used then the AUX AUDIO connector
PL7 may be used as a second CD mixer input. The AUX AUDIO connector PL7 has the same pinout as PL8. PL13 is a
serial audio link to the Audio codec. It should not be used.
LK14 DDC/12V - Monitor hardware configuration link
This link routes either a serial signal to the monitor to support the DDC "plug and play" protocol between the computer
and an attached monitor, or routes a high impedance 10V to pin 12 of the video connector as previous Acorn RISC OS
computers did. Unless this old behaviour is essential, it is recommended that the link be configured for DDC mode.
Pin
Function
1-2
High voltage signalling
2-3
DDC mode
*DEFAULT*
Page 7
PL21 SERIAL2 - second serial port
This header presents a fully buffered second serial port which is identical in function to the external port. To use this
port requires a suitable block driver and that the SER/MIDI links (LK7,13) have their jumpers set to link pins 1-2.
Pin
Function
1
DCD
in
2
RX
in
3
TX
out
4
DTR
out
5
GND
6
DSR
in
7
RTS
out
8
CTS
in
9
RI
in
10
NC
As with the external serial port, an active (positive) signal will trigger a wake-up serial event. If enabled and the machine
is in standby, the power management unit will automatically switch on the machine.
PL25 Genlock
This 2mm pitch connector is compatible with previous RISC OS computers and provides the required signals to support
Video Genlock or to drive an LCD display.
Pin
Function
1
HSYNC
out
horizontal sync
2
VSYNC
out
vertical/composite sync
3
SYNCH
in
vertical synchronization input
4
GND
5
HCLK
in
alternate pixel clock
6
ECLK
out
pixel clock
7
GND
8
ED(0)
out
digital pixel data
9
ED(1)
out
10
ED(2)
out
11
ED(3)
out
12
ED(4)
out
13
ED(5)
out
14
ED(6)
out
15
ED(7)
out
16
GND
LK8,12,15,16,19
ROM select links
These should not be altered at any time unless instructed by your supplier. The jumper default settings are:
LK8
Pin 1-2
LK16 Pin 1-2
All other links in this group have no jumper caps fitted.
Page 8
PL17,16
PRIMARY/SECONDARY - EIDE interface connectors
The two connectors provide a standard IDE interface capable of supporting up to two devices (a master/slave pair) on
each socket. Cables should be no longer than 75cm in length and be fitted to each socket so that the pin 1 markings
match. The use of "bump" polarized connectors will help in this alignment. If for any reason the cable is reversed, an
error message warning of an IDE bus fault will be given when the machine is next powered on and the interface is
disabled. Both connectors have the following connections:
Pin
Function
1
*RESET
out/OC
2
GND
3
D(7)
in/out
4
D(8)
in/out
5
D(6)
in/out
6
D(9)
in/out
7
D(5)
in/out
8
D(10)
in/out
9
D(4)
in/out
10
D(11)
in/out
11
D(3)
in/out
12
D(12)
in/out
13
D(2)
in/out
14
D(13)
in/out
15
D(1)
in/out
16
D(14)
in/out
17
D(0)
in/out
18
D(15)
in/out
19
GND
20
NC
21
NC
22
GND
23
*IOW
out
24
GND
25
*IOR
out
26
GND
27
IORDY
OC
28
Cable select
(390 Ohm to GND)
29
NC
30
GND
31
IRQ
in
32
*IOCS16
OC
33
A(1)
out
34
*PDIAG
in/out
35
A(0)
out
36
A(2)
out
37
*CS(0)
out
38
*CS(1)
out
39
*DASP
in/out
40
GND
*Signals prefixed with "*" indicate negative going logic.
Page 9
PL15 FLOPPY - dual floppy disk interface
The FLOPPY connector will support up to two standard PC floppy disk drives with a suitably twisted "swap-over" cable.
Single drives can be connected using either a straight or swap-over cable. Drives of a type used in previous RiscOS
machines may be used but care should be taken when connecting them to make sure that the drive is set to DRIVE "B"
or "1".
It is always good practice to ensure the correct media is used in the drives, ie 2Mb HD disks used for 1.6 or 1.44Mb
formats and 1Mb DD disks for 800K or 720K formats. Failure to do so way mean that your disc may not be read
correctly on another machine especially if transferring files between a RISC OS machine and a PC.
Pin
Function
2
DENSITYSEL
in/out
4
NC
6
DRATE
in/out
8
INDEX
in
10
MTR0
out
12
DRIVE1
out
14
DRIVE0
out
16
MTR1
out
18
DIRECTION
out
20
STEP
in
22
WriteDATA
out
24
WriteGATE
out
26
TRACK0
in
28
WritePROTECT
in
30
ReadDATA
in
32
SIDE1
out
34
DiscCHANGED
in
All odd pins are connected to GND
Page 10
PL3
ATX POWER - power feed from ATX PSU
A standard ATX power supply is used to feed the motherboard. Because of the board's low power consumption, it is
recommended that a PSU of no more than 145W is used or a sufficient load on it's output be guaranteed to keep the
outputs of the PSU stable.
Caution!
As the motherboard is powered continuously by the standby power supply of the PSU, before any work or upgrading is
done on the motherboard, the PSU should be disconnected from the mains and allowed to discharge fully first. This
may vary with the type of PSU used and can take up to 30 seconds. When discharged, the POWER LED will cease to
flash.
Pin
Function
1
NC
2
NC
3
GND
4
+5V
5
GND
6
+5V
7
GND
8
DC OK
9
+5V standby
10
+12V
11
NC
12
-12V
13
GND
14
*PSU Enable
15
GND
16
GND
17
GND
18
-5V
19
+5V
20
+5V
The motherboard requires the following supplies:
Voltage
Current
+5V
1A
+5V Standby
150mA to 800mA (dependant on mouse/keyboard consumption)
-5V
0 to 500mA (used for ISA bus only)
+12V
100mA (used for serial and clean audio supply)
-12V
20mA (used for serial drivers)
These ratings must be increased if expansion cards are fitted.
Page 11
SPEAKER
IRDA
LED
LK
PWR
HD
RST
WAKE
1A
11
1
1
1
1
1
1
1
1
1
1
1
LK16
LK8
LK12
LK15
LK19
VAR-FAN
12V FAN
LK1
LK2
LK17
LK18
LK6
LK11
PL22
2
9
10
1
1
1
1
40
40
34
PL12
ROMSEL1
ROMSEL0
CMOS PROTECT
AUX BAT/
RAM CLR
PL6
PL24
PL19
LK4
LK5
LK3
LK9
96B
96A
1B
PL13
PL14
PL7
CD AUX
WAVE EXPANSION
JOYSTICK2
CD AUDIO
PL8
PL11
1
1
LK14
VOLUME
ADJUST
GENLOCK
SERIAL2
1
1
10
2
9
21
6
15
PL2
PL9
IIC
1
LK7
LK13
SER/MIDI
ROM2
ROM1
EXPANSION ROM
LK10
0WB
PRIMARY
SECONDARY
FLOPPY
DRAM SLOT A
DRAM SLOT B
PIN 1
PIN 1
ISA EXPANSION
JOYSTICK/MIDI
PARALLEL
VIDEO
SERIAL
NETWORK
KEYBOARD
MOUSE
ATX POWER
1
10
11
20
2
15
16
2
25
26
28
7
SYSTEM ID
VID0
VID4
VID1
VID2
VID3
ARM 7500FE
PL5
1
VOLUME
PL17
PL16
PL15
PL25
PL21
R163
PL4
PL3
2
39
33
(LOWER)
(UPPER)
(UPPER)