2013-02-13 Sorry, these are completely sold out, and will not be manufactured in the future.
See: http://www.dontronics-shop.com/simmstick-ten-years-on.html

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Dontronics Home Page    DT107 SimmStick for 8051, 8252, AVR 8515 and AVR 28 pin Micros

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23-Jul-2002 Wayne Maeder of Telemetria/UniPage Australia. MEGA161 works in the DT107.
13-Aug-2002 Joe Stone, You might want to add a note to your web site that the ATmega163 is *not* compatible with the DT107 (the two aren't even pin compatible). It might save someone else a lot of wasted time and money.
17-Aug-2002 Mega8 is pin compatible with 28 pin socket ans should work. Feedback welcome.

Click on the Icons for Schematics in PDF or GIF format.

Assembly Instructions:
You can even change Micro types if you install a 28 pin socket in the U6 position, and two 20 pin machine pin strips into the U1 position.

Bill Of Materials:
1 by DT107 SimmStickTM PCB

1 by 78L05 VR1  +5  Voltage regulator in TO-92 case. (Optional)

1 by Capacitor C5  15pf to 22pf Ceramic (Install only if Crystal is installed)

1 by Capacitor C6  15pf to 22pf Ceramic (Install only if Crystal is installed)

1 by Capacitor C7  .01uf (or .1uf) Ceramic

1 by Capacitor C8  .01uf (or .1uf) Ceramic

1 by Capacitor C9  10uf Tantalum or Electro.

1 by Capacitor C10 4.7uf-10uf Electrolytic (PCB mount.) or Tant. @16 V. (pwr-res)

1 by Capacitor C11 .01uf (or .1uf) Ceramic

1 by Capacitor C12 .01uf (or .1uf) Ceramic

1 by Capacitor C13 .01uf (or .1uf) Ceramic

1 by Capacitor C14 .01uf (or .1uf) Ceramic
1 by Resistor  R1 10K  .25 watt (Used for power up-reset circuit.)

1 by Resistor  R2 10K  .25 watt (Res pullup and part of power-up reset).

1 by Resistor  R3 10K  .25 watt (Install only for non-AVR.)

1 by Resistor  R4 10K  .25 watt (Install only for non-AVR.)

1 by Resistor  R5 100K .25 watt (CS Serial EEPROM Pull-up)

1 by Resistor  R6 2.2K .25 watt (RS-485 Pull-down)

1 by Resistor  R7 100  .25 watt (RS-485 Network Termination resistor)

1 by PNP small signal transistor. Q1 BC558. (Install only for non-AVR.)

US Type 2N4403 can be used, however it must be rotated 180 degrees so 

that the flat side of the transistor is facing away from U5 and not 

towards it as shown on the overlay.
And either a Crystal of a suitable value, or a 3 pin Resonator. If a crystal is fitted then C5 and C6 must be installed. If you use a Resonator, then you mustn't install these two caps.

X1 Crystal or Resonator to match your clock requirements.

Optional RS-232 Serial Communications:

1 by Capacitor C1 1uf Electrolytic (PCB mount.) or Tant. @16 V.

1 by Capacitor C2 1uf Electrolytic (PCB mount.) or Tant. @16 V.

1 by Capacitor C3 1uf Electrolytic (PCB mount.) or Tant. @16 V.

1 by Capacitor C4 1uf Electrolytic (PCB mount.) or Tant. @16 V.

1 by MAX-232 U2 (or equivalent)

It may also pay to install a 16 pin socket for the Max-232, 

as you may have to remove it for some configurations.
Optional RS-485 Serial Communications:
1 by MAX-485 U4 (or equivalent)

If you install a 28 pin Micro, you will have to choose a signal to control the 485 chip, by jumpering a wire between sockets of the micro and 485 chip.

Optional SPI Serial EEPROM
1 by AT25256 U3

Brown-Out Circuit:
This small IC (U5) in a TO-92 package is used to stop the Micro operation becoming unpredictable during a power 'brown-out'. In most cases this isn't required. It's just an added precaution for reliable operation. The older Atmel micros may well need this device.

By just simply ignoring the brown-out circuit and installing resistors R1 and R2, the circuit operation should be fine.
R1, and R2 must be installed at all times for normal operation. Yes, even if you don't use a brown-out circuit.

If you wish to use the brown-out circuit, it's just added to the board, and can be either a CMOS or Open Collector type.
You can use the following I.C.'s:
Panasonic MN13811-S (Open Collector)
Panasonic MN1381-S (CMOS)
Zetek ZM33064
Motorola MC33064/P
Other types may also be suitable. These should switch at between 4.2 and 4.6Volts. This is for +5 Volt operation.

Status LED One (Optional)
LED1  1 x 3mm LED.
R9    1 x Resistor  1K .25 watt

Kanda Compatible Connector (Optional)
J4    10 pin IDC Connector. (2 x 5 male header).
LED2  1 x 3mm LED.
R8    1 x Resistor  1K .25 watt

AVCC: (Used for A/D 28 pin Micros) (Optional)
C15   1 x Capacitor .1uf (100nf) Ceramic
R10   1 x Resistor 100 .25 watt

Resistor Network RP1 for Non AVR
9 x 10K Resistors, 10 pin device.
Connects pins 31 to 39 of the micro to VCC via 10K Pull-ups.
We figure on using a 10 pin resistor network and installing it in a sil socket if you want to use non-avr then avr on the same board. We have allowed for pin 31 in this network. See schematic.
Pin 31 needs the option to be pulled high for the AT89s8252.
Pin 31, EA / VPP, needs option to be tied to vcc for internal program execution.


Header block for unused gates of the MAX-232. These are spares, but can be useable if jumpered correctly for other handshaking RS-232 lines.

Used to Isolate the +5V signal on the edge connector from the 78L05 regulator output if it is installed. Both outputs should never be used together. A test link and two male posts are used to reinstall the regulator output. Default open.

Used to connect, or swap RS-232 and RS-485 connections to the Micro.
This may be be understood in conjunction with a schematic in front of you.

"A" Comms is the section that deals with RS-232 signals.
"B" Comms is the section that deals with RS-485 signals.

To connect the hardware UART of the micro to the SI and SO signals,  you need to connect JP3 pin 3 to pin 5, and pin 4 to pin 6. This also connects these signals to the on board MAX-232 if installed. This is basically how most other SimmSticks are set.

To connect a "Software bit-banged" UART of the micro to the RS-485 circuitry, you need to connect JP3 pin 7 to pin 9, and pin 8 to pin 10.

To connect the hardware UART of the micro to the RS-485 circuitry,  you need to connect JP3 pin 1 to pin 3, and pin 2 to pin 4.

To connect a "Software bit-banged" UART of the micro to the MAX-232, you need to connect JP3 pin 5 to pin 7, and pin 6 to pin 8.

Connect pin 1 to pin 2 for AVR operation, and pin 2 to pin 3 for Non-AVR operation. This uses Q1 to invert the reset signals to match the Simm Bus.

Used to terminate the RS-485 Network. Default open.

SimmStick Bus.

RJ-45 Connector for RS-485 Comms.

40 pin header, pin for pin layout reverse compatible with 40 pin Micro.
Also used for Ram Sandwich.
If a 40 pin header is used in position J3, then the setup can be effectively used as an emulator. But watch out for pin crossover. If you crimp a 40 wire cable with a .6" DIP connector one end, and a .1" by 2 rows of 20 pins IDC type connector the other, you will find that the 40 pin male header (J3) on the DT107 board is the correct way around.
The pinout doesn't correspond to the Micro pinout as there must be a crossover.
Please beleive me that this happens in 99% of cases.

Kanda Programming header.

1 x 3 pin header. 1 test Link. Configure AREF to VCC for 28 pin micro.

Comments and Corrections welcome!

5-Nov-2000 Brian Millier wrote:

Hi Don:  I got the parts needed to finish the DT107 and tried it > out with the BasicX. No luck- dead as a nit on the simple "hello world" program. I tracked the problem down to the fact that there was no connection between the serial EEPROM pin 2 and the 8515 pin 7. When I wired that up, things worked OK. Luckily you had sent me 2 PCBs so I was able to track down the offending trace on the unpopulated board. It turns out that both my boards share the same problem. If you follow the trace outlined above, it leads to a via that is between R5 and R6. It is the second via up from the SIMM bus, ( if you just count the vias actually between the two resistors.) These vias are awfully small so I hope that this will not be a fabrication problem for the PCB company.

While I did not extensively test the RAM sandwich functionality, I did put a RAM write loop into the program, and it passed through that OK. ( program dies if the RAM sandwich is not present or working). Thought I'd better let you know about this quickly, in case this flaw is present in all boards.
Brian Millier
Technical Manager
Chemistry Department
Dalhousie University
Halifax, N.S. B3H 4J3

Hi Brian.
We had to reduce the via pads and hole sizes just to get the board to route. My board man "Mick" pulled his hair out over this one.
see: http://www.dontronics.com/graphics/mik2.jpg I just checked 10 random boards and they are all OK, but of course no guarantee. It was the physical plated through on that via hole then was it?

OK, I just checked many more, but I'll add a little note. Not everyone will fit a basicx or ram sandwich, but if they do and it doesn't work, this will assist a lot. And they may well want to fit the serial EEProm anyway.

Cheers Don...

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