LAWICEL Soft- & Hardware

The picture above shows 2 Simm100 boards (component and solder side)
for the Atmel AVR microcontroller type AT90S8535.

The picture above shows the Simm100 board mounted with an AT90S8535, MAX232, MAX701, Reset button and IDC connectors for RS-232, ADC and ISP (In System Programmable). To improve EMI, the board has a ground layer and a separate ground layer for the ADC for a stable Analog Conversion.

REV.A Schematics

REV.B Schematics

SIMM100 REV.B was made in August 2000.

2 wires for RS232 added to the standard A1/A2 pins.
New RESET devices added

The picture above left shows that it is now possible to add a standard Brown out reset device (similar to those used on e.g. DT103/104/107). Since the normal MAX701 has a separate input pin and an output pin for reset, you need to connect these signals together and that is done with the jumper.

Assembling Instructions

For minimum operation you have to install IC1, XTAL, C1, C2, C3, C11, C12 & R3. The XTAL can be exchanged to a resonator, then C2 and C3 can be omitted. When using the RC Reset (C12 / R3), you also need to install jumper J6 (Rev.B board only) or jumper pin 1 & 6 of IC3 (Rev.A board only) , so the reset signal reaches the microcontroller. You can also add the PB1 pushbutton for a manual RESET if you do not have that on any other place (like e.g. on the DT003/DT006).

If you need a bit better RESET (due to that you have other hardware in the system like EEPROM etc. and you want to guarantee that the microcontroller doesn't write to the EEPROM when voltage is too low, then you shall install the Brownout device Q1 and the resistor R6 (Rev.B board only).

If you need the best RESET performance with a delayed RESET of 200-300mS, you should not install C12 / R3 or Q1 / R6, instead just install the IC3 (MAX701).

Then if you need ISP (In System Programmable) with a Kanda / Atmel STK200 compatible programmer, you need to install J2 and if you like to have indication when programming etc. also R2 and LD1.

If you want to use the ADC of the AT90S8535, then install R1 and C4 and optionally the J2 IDC connector. Jumper J1 is by default applying 5VDC to the AREF of the ADC and if you need any other reference voltage, cut that wire open on the board and install J1, so you can select a different reference voltage. pin 9 on the J1 connector could then be used for applying the new voltage reference. There is also a very small Prototype/Experiment area and one of the pads are connected to 0VDC (GND) and the other 5VDC (VCC).

To add on board RS-232, you need to install IC2, C5, C6, C7, C8, C9 and the J4 IDC connector. The J4 IDC connector is pin compatible with the SLI-OEM from Wirz (SLI-OEM was removed from Wirz line 2004), so adding a straight ribbon cable between the SIMM100 and the SLI-OEM makes it simple and easy to use a serial LCD.

If you do not have access to 5VDC and would like to use e.g. 9-12VDC then install the voltage regulator V1 and capacitor C10.

Finally the 2 user definable / general purpose LEDs (LD2 & LD3) plus the resistors for them (R4 & R5) could be mounted and controlled via PC0 & PC1 of the microcontroller, note that they sink current into the microcontroller, so turning them on need a LOW output (0VDC) and turning them off needs a HIGH output (5VDC).

J5 is also a small 4 pin connector for the rest of the PD port (PD4-7) that isn't routed out the the SimmStick bus.

Component Values

IC1	Microcontroller type AVR AT90S8535 or simular
IC2	RS-232 Tranceiver type MAX202/232
IC3	Reset circuit type MAX701
C1, C4, C9, C10, C11	100nF (same as 0.1uF)
C2, C3	22pF (15-30pF)
C5, C6, C7, C8	1uF (if MAX232) or 0.1uF (if MAX202)
C12	4.7uF to 10uF depending on reset delay
R1	100 ohms
R2, R4, R5	1k ohms
R3	10k ohms
R6	10k ohms (Rev.B only)
XTAL1	What ever frequency you need (Chrystal or Resonator)
V1	5VDC/1A voltage regulator type TO220 with screw for proper cooling
LD1	LED for indicating ISP programming, normally 3mm RED
LD2, LD3	LEDs for general purpose 3mm, color is up to you
J1	Jumper 3*1 pins
J2,J3,J4	10pin IDC connector
J5	Connector 4*1 pins
J6	Jumper 2*1 pins (Rev.B only)
PB1	Reset push button
Q1	Brownout (Rev.B only) type Panasonic MN13811-S (O/C) or similar.

Demosoftware written in BASCOM-AVR is availible in zip format here (includes Basic source file and hex file). This simple program demonstrates how the on-board LED's can be turned on and off.

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