Schematics

Here you can download the schematics as PDF-file. If you use Ulticap, you can download the (compressed) UTSCH-file.

Memory

The lower 8 address-lines are (as usual) generated by a 74HC573 (IC3) from the data bus, controlled by the address-latch-enable-line. The program memory consists of a 128kB flash-ROM (29C010). When it is easier to get a 29F040, this can also be used, but the additional memory cannot be used. Furthermore the board has 32kB of RAM, which can be used as data or as program memory, depending on the operating mode of the board.

Watchdog

IC9 is a watchdogtimer from Maxim with several functions. On power-on a reset pulse is generated. When the supply voltage drops below the usable range or breaks down completely, the chip-enable-signal to the RAM is disconnected and power to the RAM is supplied by the backup battery.
The controller can check the battery status using the PFO-pin. Finally the controller can toggle the watchdog at the WDI-input, from which also a reset can be generated. This feature is disabled if R15 and R16 are left open.

Chip-select-signals

On K2 there are 8 chip-select-signals (/CE0-/CE7) which are generated by IC7. These can be used to controll memory-mapped-IO, when also connecting /WR or /WR. The signals are addressed in the range 0x8000 - 0x8007. Should they not be enough, you can use the signal /CE_IO1 in the address range 0x8800 - 0xF7FF to connect more IO.

I²C-bus

When the I²C-bus is needed, the resistors R1-R4 must be populated like in the schematic. If not, you should use 0R for R1 and R2 and 10k for R3 and R4, because P1.6 and P1.7 have no internal pull-ups.

Jumper

R1	With P1.2 (when R1 is populated) or with P4.2 (R2) the board can switch between debug and run mode.
R2
R5	If R5 is populated, the internal watchdog is enabled, populate R6 to disable it.
R6
R7	If R7 is populated, then P1.0 is used to switch between normal and programming mode. Which R8 P4.0 is used.
R8
R11	If R11 is populated, the 5V supply voltage is the reference voltage for the AD-converter. If this is not accurate enough, leave the jumper open and connect the reference voltage to pin 35 of K1.
R12	Signal ground for the AD-converter is connected to digital ground with R12. The ground of an external reference voltage can be connected to pin 34 of K1.
R13	When the power supply voltage drops below 4.6V, the /PFO-pin switches to low. With R13 and R14 you can choose which interupt is generated. This maybe makes it possible to do something before the supply voltage becomes to low and the controller if forces into reset by the MAX691.
R14
R15	If you want to use the watchdogfunction of IC9, you must populate either R15 or R16. This defines with which portpin the watchdog is toggled.
R16