P112 CPU Board Support

Parts List
 22pF ceramic        4    C1, C2, C25, C26
 120pF ceramic       1    C12
 100nF bypass        14   C3, C15, C16, C17, C18, C19, C20, C21
                          C22, C23, C24, C28, C29, C30
 1uF, 16V tant.      9    C4, C5, C6, C7, C8, C9, C10, C11, C27
 22uF, 10V tant.     2    C13, C14
 7x220 respack       1    U13
 7x2k2 respack       1    U14
 7x47k respack       2    U16, U17
 4k7 resistor        1    R11
 10k resistor        3    R5, R7, R10
 27k resistor        1    R9
 47k resistor        8    R1, R2, R3, R4, R6, R8, R12, R13
 2-pin Hdr           2    P5, P11
 3-pin Hdr           3    P1, P12, P13
 5-pin Hdr           2    P2, P6
 2x2-pin Hdr         1    P3
 2x5-pin Hdr         2    P4, P8
 2x10-pin Hdr        1    P14
 2x13-pin Hdr        1    P7
 2x17-pin Hdr        2    P9, P10
 PCB jumper          10
 DIN48 skt.          1    J1          (3x16-way half-DIN skt)
 32DIP skt.          3    U2, U3, U4
 32kHz crystal       1    Y2          (RTC crystal)
 16MHz crystal       1    Y1          Parallel resonant (CPU clock)
 24MHz crystal       1    Y3          Parallel resonant (IO chip clock)
*BAR43C diode        1    D1          (Schottky)
*BAR43  diode        1    D2          (Schottky)
*BCW71  transistor   1    Q1
 28F256A             1    U4          (Intel Flash ROM, programmed)
 74HCT00             1    U5
 74ACT02             1    U8
 74ACT139            1    U11
 62256               2    U2, U3      (Static RAM, 32kB)
 DS1202              1    U6          (Dallas RTC chip)
*FDC37C665IR         1    U9          (SMC Super-IO chip)
 LT1133              2    U7, U10     (Linear Technology RS232 Tx/Rx)
 NMF0512S            1    U12         (Newport Components Flash ROM power)
 TL7705ACP           1    U15         (Texas Insts. Reset genr.)
*Z8018216            1    U1          (Zilog CPU chip)
 3.7V battery        1    B1          (Lithium Thionyl Chloride, 1/2AA)
Parts prefixed * are pre-installed on the board.

You can use the fast SRAM chips out of PC motherboard caches in this board. Just spread the pins and solder them on to a 32-DIP header. Then plug in the board.

Be sure to use fundamental mode crystals, not overtone types. Overtones will run at the wrong frequency, and will cause 'Non-standard CPU clock crystal...' messages on start-up. Note that the CPU crystal will always "get the blame" in this message, regardless of which crystal is actually wrong.

In very rare cases, some 24MHz (IO chip) crystals have proved reluctant to start. This can be overcome by putting a high-value resistor (say 5 - 10M) across the crystal.

Likewise, check you have the right type of resistor networks. There are 2 types in those 8-pin SIL packs: 7 resistors with a common pin, and 4 independent resistors. P112 uses the 7 commoned resistors.

There are two kinds of "lithium" battery available: 3.0V Lithium Manganese, and 3.6/3.7V Lithium Thionyl Chloride. They have the same PCB footprint, but the opposite polarity (ugh!). The P112 board uses the Lithium Thionyl Chloride types.

The D-X Designs' P112 CPU Board Support Site

Parts List