CPU Front Panel

CPU Front Panel

ELF Membership board:

3.5" x 2.15" (fits in an Altoids candy tin)

1802 CPU (with adjustable RC clock oscillator)

one 28-pin memory socket (for standard 2k-32k byte RAMs or EPROMs)

8-bit output port (OUT5 or OUT7)

8-bit input port (IN5 or IN7)

expansion header with all I/O and 1802 signals

operates on 3v-6v at under 1ma (plus whatever the particular memory chip you use requires)

ELF Front Panel board:

3.5" x 2.15" (plugs onto the Membership board)

9 individual LEDs (D0-D7, plus Q)

11 subminiature toggle switches (D0-D7, Clear/Wait/Load/Run, and Memory Protect -- exactly like original ELF)

25-pin DB25 connector to go to PC parallel port

The PC connection allows the PC to completely control the front panel; and thus load, examine, and run programs, and read/write to the I/O ports.

Parts List

Membership board parts list: [revised 3/22/10]

C1      22pf NPO ceramic capacitor, 0.1" lead spacing

C2-4,6  0.1uF Z5U or X7R ceramic capacitor, 0.1" lead spacing

C5      0.047 farad 5.5v memory backup capacitor, 0.465" dia, 0.2" lead spacing (PC board hole too big)

D0-8    LED, T1-3/4, color of choice

D9,10   signal diode, 1N4148 etc.

D11     zener diode, choice:

1N5231B 5.1V (cheap but uses higher current)

or 1N5232B 5.6V (use with regulated 5V supply)

or 1N4625 5.1V low poer zenor (micropower)

J1      30-pin header, 0.025" square pins on 0.1" centers (wirewrap length preferred)

J2      DB25F female 25-pin D connector, with #4 mounting hardware

J3-6    jumpers, .1" spacing, to short pins in P2 and P3 (configuration for U2)

P1abc   MOlex KK top entry socket, 10 pin, Digikey WM3241-ND (need 3)

P2      5-pin header, 0.025" square pins on 0.1" centers, from 36-pin header

P3      4x2 pin header, 0.025" square pins on 0.1" centers (2 removed)

P4      4 pin header, 0.025" square pins on 0.1" centers

R1      trimpot, Bourns 3266W or eq, 0.25" square, 0.1" lead spacing

R2      15k 5% 1/4w resistor

R3,6    100k 5% 1/4w resistor

R8-10   470k 5% 1/4w resistor <---changed 3/22/10 HRJ see this note

R4      470k 5% 1/4w

R5      100k x 8, 9-pin SIP, one side bussed

R7      1meg 5% 1/4w resistor

R11     1K 10-pin SIP, 9X1K

R12,13  100K 8 pin SIP, 7 X 100K

S0-10   submini toggle switch SPDT right angle (Digikey KCN1059-ND, $5+)

S11     submini momentary switch SPDE (Digikey CKN1740-ND, $4.87)

U1      CMOS CPU, CDP1802, use 40-pin low profile socket (Mouser 575-393640, $4)

U2      2k-32k CMOS RAM (6116, 6264, 62256) or EPROM (27C16-27C256)

        use 28-pin low profile socket (Mouser 575393628, $3)

U3,7    CMOS octal latch, 74HC373

U4      CMOS quad 2-input NAND gate, schmitt trigger, 4093

U5      CMOS dual D flip-flop, 4013

U6      CMOS octal buffer, 74HC244 or 74AHCT244

U8      CMOS 4071 quad 2-input OR

U9      CMOS 74HC257 multiplexer

Front panel board:

C6      0.1uF Z5U or X7R ceramic capacitor, 0.1" lead spacing

D0-D8   LED, T1-3/4 high brightness

J2      DB25F female connector, PC mount

P1      30-pin female top entry socket for J1, Molex KK series

    Molex 22-18-2101 (10-pos; use 3)

P4      4-pin header, 0.025" pins on 0.1" centers

R8-10   100k 5% 1/4w

R11     1k x 9, 10-pin SIP, one side bussed

R12,R13 100k x 7, 8-pin SIP, one side bussed

S1-10   SPDT toggle switch, C&K T101 series

S11     SPDT pushbutton switch

U8      CMOS quad 2-input OR gate, 4071

U9      CMOS quad data selector, 74HC257

Altoids brand, tin candy box