
                         Guide to the HP48G/GX Hardware
                          Compiled by  Philippe Teuwen
                     --------------------------------------
                     Version 0.04        22th Novembre 1996


0.      Table of contents
        -----------------

        1.  Introduction
        2.  Global View
        3.  Pinouts Description
        4.  74HC174: Hex D-type flip-flop with clear
        5.  74HC00:  Quad 2-input NAND gate   
        6.  RAM 32k or 128k & ROM 512k
        7.  Ports    
        8.  Drivers for LCD  
        9.  Keyboard 
       10.  LCD Display 
       11.  Yorke Chip
       12.  Printed Circuit Board
       13.  IR Reception
       14.1 IR Transmission for the S/SX
       14.2 IR Transmission for the G/GX
       15.  RS232 Description
       16.  Power Supply
       17.  Backup Power Supply
       18.  Miscellaneous
       19.  Contacting the author


1.      Introduction
        ------------

These shematics result from personal observations.
So any warranties are provided about the content of this text.
Please notify me of any errors (about language too!) or omissions
or to complete some points like official pins names and uses
or bad known devices.
This text can be freely distributed but please don't modify it yourself.
Simply tell me what's wrong and I'll correct it for everybody.
All is shown from the back, batteries towards you unless
you hear to the contrary.
Some parts exist only on GX calculators.


2.      Global View
        -----------

            -----!!!!----OO-----     Serial connector/LED IR/Recv IR
           |      &             |
           | XXXX XXXXXXXX XXXX |    the processor between 2 LCD drivers
           | XXXX XYORKEXX XXXX |
           | XXXX XXXXXXXX XXXX |    & (4): jumpers
           |      XXXXXXXX &    |
           |     &        RX  H |    crystal (32kHz time X'tal)
           |         &    IR  H |    RX IR Circuits
  RS232    |T                   |
    TX     |X ################  |    Expansion connectors    ___________
 Circuits  |R ################  |    (port2 upside)      ___| port 2    |
           |S ################  |                       /   |___________|__
           |  !!!!!!!!!!!!!!!!  |    small wires       /  __| port 1       |
   Alim    |A                   |                   __/__/__|______________|__
 Circuits  |L  74 XXXX XXXX  CC |    RAM/ROM/Capacitor 1mF
  74HC174  |I  HC RAMX ROMX  HC |    74HC00                       
           |M     XXXX XXXX  00 |                  
           |--------------------|
           | +                  |
           |                    |    Battery Case
           |                  - |
            -------------------


3.      Pinouts Description
        -------------------

A0-A16:    Address lines
A17-A21:   Extended lines for port 2  (A18 is inverted, actually: NA18)
AR17-AR18: Extended lines for ROM
BEN:       Bank Switching Enable
buzz:      Buzzer (the second line of the buzzer is grounded)
CDT1-CDT2: Card Detect Type for port 1-2 (H:RAM L:ROM X:No Card)
CE1:       Card Enable 1 (In GX, is used to enable A17-A21 for port 2)
CE2:       Card Enable 2 (In GX, is used as CE for port 1)
CE2.2:     Card Enable port 2 (Not from CPU; CE2.2=BEN*N(AR18) )
D0-D7:     Data lines
GND:       Ground
LD(0):     Display: The first bit of display information
LD(1):     Display: The next bit
LP:        Display horiz sync (Fall. edge: a new line is about to be started)
NC:        Not Connected
NCE0:      Card RAM Enable
NCER:      ?Card ROM Enable
NOE:       Original Output Enable (Not used in G/GX)
NOE2:      Output Enable for all RAMs and ROM (Not from CPU; NOE2=N(NWE) )
NWE:       Write Enable for all RAMs
ON-key:    ON-key is wired directly to CPU
RX:        RS232 Reception
RXir:      IR Reception
SPD:       Processor Speed (H:4MHz L:2.4MHz)
sync1:     ?Display sync line (between both drivers)
sync2:     ?Display sync line (between both drivers)
sync3:     ?Display sync line (between both drivers and the CPU)
sync4:     ?Display sync line (between both drivers and the CPU)
sync5:     ?Display sync line (between both drivers and the CPU)
TX:        RS232 Transmission
TXir:      IR Transmission
V1-V299:   Display data lines for the LCD
Vbb1-Vbb2: Card battery check (L:warning low bat port 1-2)
Vcc(on):   =5V  if HP is turned on else =0V
Vcc(10):   =10V if HP is turned on else =4.5V(bat)
Vcc:       =5V  if HP is turned on else =4.5V(bat)
+4.5V:     Directly wired from battery + pin
x3:        ? (links 84 and 124 of the CPU and alim circuits)
x4:        ? (links 128 of the CPU and alim circuits)
XSCL:      Display clock (Falling edge: 2 bits of display data may be read)
Xtal1:     To X'tal 32kHz
Xtal2:     To X'tal 32kHz
(GND):     \                              Ground
(RX):       | Pinouts of the RS232 I/O    Reception
(SH):       |                             Shield
(TX):      /                              Transmission


4.      74HC174: Hex D-type flip-flop with clear  ( Only on GX )
        ----------------------------------------

           -----------
     CE1 -| CLK   GND |- GND         NCLR CLK D Q
     BEN -| 4Q     3Q |- A17           L   X  X L
      A5 -| 4D     3D |- A0            H   ^  H H
     A21 -| 5Q     2Q |- A18           H   ^  L L
      A4 -| 5D     2D |- A1            H   L  X Q0
      A3 -| 6D     1D |- A2
     A20 -| 6Q     1Q |- A19       /-- 47k ---- Vcc(on)
  Vcc(on)-| Vcc  NCLR |- Vcc 3V --< 
           ----/^\---- 1           \-- 100k --- GND


5.      74HC00: Quad 2-input NAND gate  ( Only on GX )   
        ------------------------------

           ----\_/---- 14
  Vcc(on)-| 1A    Vcc |- Vcc(on)    
    AR18 -| 1B     4B |- Vcc(on)     Logic:   Y=N(A*B)
4(HC00) /-| 1Y     4A |- NWE                 
3(HC00) \-| 2A     4Y |- NOE2        Results: CE2.2=BEN*N(AR18)
     BEN -| 2B     3B |- 6(HC00)              NOE2=N(NWE)
10(HC00) -| 2Y     3A |- Vcc(on)              
     GND -| GND    3Y |- CE2.2
           ----------- 


6.      RAM 32k(G) or 128k(GX)                  ROM 512k
        ----------------------                  --------

             -----------                       -----------
        D3 -| D3    GND |- GND            D3 -|           |- GND 
        D4 -| D4     D2 |- D2             D4 -|           |- D2 
        D5 -| D5     D1 |- D1             D5 -|           |- D1 
        D6 -| D6     D0 |- D0             D6 -|           |- D0
        D7 -| D7     A0 |- A0             D7 -|           |- A0 
      NCE0 -| NCE    A1 |- A1           NCER -|           |- A1
       A10 -| A10    A2 |- A2            A10 -|     ?     |- A2
       GND -| NOE    A3 |- A3            GND -|           |- A3
       A11 -| A11    A4 |- A4            A11 -|           |- A4
        A9 -| A9     A5 |- A5             A9 -|           |- A5
        A8 -| A8     A6 |- A6             A8 -|           |- A6
       A13 -| A13    A7 |- A7            A13 -|           |- A7
       NWE -| NWE   A12 |- A12           A14 -|           |- A12
       Vcc -|CE/Vcc A14 |- A14          AR17 -|           |- A15
          28 ....:^:.... 1   if 32k     AR18 -|           |- A16
                                      Vcc(on)-|           |- GND
       A15 -| A15   A16 |- A16              32 ----/^\---- 1
       Vcc -| Vcc    NC |- GND
          32 ----/^\---- 1   if 128k        Address: 512k=2^19 A0-AR18


7.      Ports  ( Only on GX )    
        -----

          port1         port2
        -----------------------
        1 Vcc(on)       Vcc(on)
        2 Vbb1          Vbb2
     3-19 A0-A16        A0-A16
       20 NWE           NWE
       21 CE2           CE2.2
       22 NOE2          NOE2
    23-30 D0-D7         D0-D7
       31 AR17          A17
       32 AR18          A18
       33 XSCL          A19
       34 LP            A20
       35 LD(0)         A21
       36 LD(1)         BEN
       37 CDT1          CDT2                   
       38 NC            NC       In Seiko-Epson Cards: Card Present       
       39 NC            NC                             Card Type
       40 GND           GND


8.      Drivers for LCD  
        ---------------

Refs: SED1181Fla Japan

          Left(reversed)  Right
      -----------------------------
     1-28 V254-V281       V222-V249
       29 sync2           NC
       30 NC              NC
       31 NC              NC
       32 LD(0)           sync1
       33 LD(1)           sync2
       34 XSCL            XSCL      
       35 LP              LP
       36 sync3           sync3
       37 V87             V52
       38 V86             V51
       39 V85             V50
       40 V83             V49
    41-50 V82-V73         V47-V38
       51 V71             V37
       52 V70             V36
    53-62 V69-V60         V34-V25
       63 V58             V24
    64-68 V57-V53         V22-V18
       69 sync4           sync4
       70\sync5           sync5
       71/sync5           sync5
       72 Vcc             Vcc
       73 Vcc(10)         Vcc(10)        
       74 sync1           NC
       75 NC              NC
       76 NC              NC
    77-80 V250-253        V218-221


9.      Keyboard 
        --------

Refs: MXS 00048-80038
! on the other side of the PCB, so X'tal is on the left

        1 Vcc           7 A3           13 A1
        2 ON-key        8 A11          14 A15
        3 A5            9 A12          15 A16
        4 A4           10 A2           16 A0
        5 A10          11 A13          17 AR17
        6 A9           12 A14

 Pressing a key makes a shortcut between 2 lines.

 Correspondance Table:

 -----------------------------------------------
| A     | B     | C     | D     | E     | F     |     ML correspondances:
|-------|-------|-------|-------|-------|-------|
| O A10 | O AR17| O AR17| O AR17| O AR17| O AR17|     OUT: #001 -> A9
| I A4  | I A4  | I A3  | I A2  | I A1  | I A0  |          #002 -> A10
|-------|-------|-------|-------|-------|-------|          #004 -> A11
| MTH   | PRG   | CST   | VAR   | up    | NXT   |          #008 -> A12
|-------|-------|-------|-------|-------|-------|          #010 -> A13
| O A11 | O A16 | O A16 | O A16 | O A16 | O A16 |          #020 -> A14
| I A4  | I A4  | I A3  | I A2  | I A1  | I A0  |          #040 -> A15
|-------|-------|-------|-------|-------|-------|          #080 -> A16
| '     | STO   | EVAL  | left  | down  | right |          #100 -> AR17
|-------|-------|-------|-------|-------|-------|     IN: #0001 -> A0
| O A9  | O A15 | O A15 | O A15 | O A15 | O A15 |         #0002 -> A1
| I A4  | A A4  | I A3  | I A2  | I A1  | I A0  |         #0004 -> A2
|-------|-------|-------|-------|-------|-------|         #0008 -> A3
| SIN   | COS   | TAN   | sqrt  | Y^X   | 1/X   |         #0010 -> A4
|-------|-------|-------|-------|-------|-------|         #0020 -> A5
| O A12 | O A14 | O A14 | O A14 | O A14 | O A14 |         #8000 -> ON-key
| I A4  | I A4  | I A3  | I A2  | I A1  | I A0  |
|---------------|-------|-------|-------|-------|
| ENTER         | +/-   | EEX   | DEL   | back  |
|---------------|-------|-------|-------|-------|
| O A13         | O A13 | O A13 | O A13 | O A13 |
| I A4          | I A3  | I A2  | I A1  | I A0  |
|---------------|-------|-------|-------|-------|
| alpha         | 7     | 8     | 9     | /     |
|---------------|-------|-------|-------|-------|
| O A12         | O A12 | O A12 | O A12 | O A12 |
| I A5          | I A3  | I A2  | I A1  | I A0  |
|---------------|-------|-------|-------|-------|
| shift left    | 4     | 5     | 6     | *     |
|---------------|-------|-------|-------|-------|
| O A11         | O A11 | O A11 | O A11 | O A11 |
| I A5          | I A3  | I A2  | I A1  | I A0  |
|---------------|-------|-------|-------|-------|
| shift right   | 1     | 2     | 3     | -     |
|---------------|-------|-------|-------|-------|
| O A10         | O A10 | O A10 | O A10 | O A10 |
| I A5          | I A3  | I A2  | I A1  | I A0  |
|---------------|-------|-------|-------|-------|
| ON            | 0     | .     | SPC   | +     |
|---------------|-------|-------|-------|-------|
| O +Vcc        | O A9  | O A9  | O A9  | O A9  |
| I ON-key      | I A3  | I A2  | I A1  | I A0  |
 -----------------------------------------------



10.     LCD Display 
        -----------

Refs: LD-F8845A-23 363D Epson Japan
! on the other side of the PCB, so X'tal is on the left

        up: 1-105 : V1-V105
        down: 201 : V201
              202 : NC
          203-297 : V203-V297
              298 : NC
              299 : V299


11.     Yorke Chip
        ----------

Refs: 00048-80063 D3004GD NEC Japan

        1 NC                    90 NWE                137 LD(0)
        2 NC                    91 RESET (if low)     138 LD(1)
        3 TXir               92-99 D0-D7              139 V88
     4-18 V217-V203            100 AR17               140 V282
       19 V201             101-117 A16-A0             141 V89
    20-35 V16-V1               118 Xtal2              142 NC
       36 NC                   119 Xtal1              143 sync5
       37 SPD                  120 NC                 144 sync4
       38 NC                   121 NOE                145 +4.5V
       39 V84                  122 TXir               146 Vbb2
       40 V72                  123 GND                147 Vbb1
    41-56 V90-V105             124 x3                 148 Xtal1
       57 V299                 125 Vcc                149 Xtal2
    58-72 V297-V283            126 Vcc(on)            150 CDT1
    73-80 NC                   127 NCER               151 CDT2
       81 RX                   128 x4                 152 V17
       82 TX                   129 -1.5k-buzz         153 V23
       83 XSCL                 130 Vcc(10)            154 V35
       84 x3                   131 TX                 155 V48
       85 AR18                 132 GND                156 V59
       86 ON-Key               133 RX                 157 V72
       87 CE2                  134 XSCL               158 V84
       88 CE1                  135 LP                 159 GND
       89 NCE0                 136 sync3              160 RXir


12.     Printed Circuit Board
        ---------------------

Refs: 00048-80050
Some tracks are interlaced to allow to solder a bridge on it.
(cf the 4 "&" on my PCB shematic)
These jumpers exist to allow to construct easily a SX with this PCB.

 Left one   :   CE1<->CE2.2
 Rigth one  :   NOE<->NOE2
 Middle one :   SPD<->Vcc   CPU at 4MHz  (soldered originally) 
 Upper one  :   SPD<->GND   CPU at 2.4MHz

! Never solder these two last ones at the same time.


13.     IR Reception
        ------------

Rem: schema picked up from HP I/O Technical Interfacing Guide

                            +5V
                _________________________________________________
               |                           |                     |
        10K    \                      18K  \               1M    \
        1/8 W  / R6                   1/8W /  R8           1/8W  /  R7
               \                           \                     \
RXir ----------|                           |                     |
               |                            \                    |
               |                             \|                  |
                \                        Q4   |------------------|
                 \|           R4             /|                  |
             Q3   |----------/\/\/----------V    <---,           |
                 /|     |   220K            |       '-----       |
                V       |   1/8 W           |                    |
  +5V _  ____   |       |                   |                    |
       ||       | 560K  /  R5        220K   /                    |
       ||       | 1/8W  \            1/8W   \  R3                /
  GND  --       |       /                   /                  |/
                |       |                   |------------------|  Q2
                |       |                   |                  |\
                |       |           .022uF ---  C1               V
                |       |                  ___                   |
                |       |                   |                    |
                 ---------------------------|--------------------
                                         ---|---
                                          --|--
                                            -
              Q4: Receiver              Q1,Q2,Q3:  2N3904      
       Refs: EG&G VATEC VTT 9112        R3-R8: 5%
                 ___
                | i |
                |i|i|
                 |||
                / | \
               E  B  C


14.1    IR Transmission for the G/GX
        ----------------------------

                       ,-->                  __
                      --'                   |  |
            +4.5V --A->|-K--- TXir          |__|
                                             ||
                                             | \
                                            /   K
                                           A

14.2    IR Transmission for the S/SX
        ----------------------------

Rem: schema picked up from HP I/O Technical Interfacing Guide

                          +5V
                          ---
      Transmit Circuit     |
                39Ohms     /
                1/8W       \  R1        
     +5V ..                 /            
         ||                |             CR1: NEC SE303A
         ||              -----  --,           or
   GND  -  ------   CR1   \ /    '-->         HP HEMP-3301 (narrower beam)
                          ---
                           |             R1-R2: 5%
                           /
OUT            R2        |/
--------------\/\/\------| Q1
---->         500 Ohms   |\
              1/8 W        V
                         -----
                          ---
                           -


15.     RS232 Description
        -----------------

      Pinout:    I__|__|__|__|__I
                    |  |  |  |
                   /   |  |   \
                (SH) (TX)(RX) (GND)

       1nF
(SH)---| |--- GND
      
  
(TX)--------------------------------
          |                         |
         --- 1nF                   / \
         ---                      /   \
          |          Vcc         |     |         Vcc
        --|--         |         \ /   ---         |
         -|-          |         ---   / \         |   2 diodes
          -           \          |     |          \
                  47k /          |     |          / 47k
                      \         /       \         \
                      |       |/         \|       |
        NPN           |-------|           |-------|          PNP
    Transistors       |       |\         /|       |      Transistors
      ref:1AM         |         V       A         |        ref:2A
                       \         |     |         / 
                        \|       |     |       |/
                         |-------|-----|-------|
                        /|          |          |\
                       V            \            A
                      |             / 150ohms     |
                      |             \             |
                      |             |             |
                      |-------------|-------------|--------- TX
                                    |
                                   ---
                                   / \    ref:H2M
                                    |
                                  --|--
                                   -|-
                                    -
        5.6k
(RX)----/\/\/--------------- RX
                |
        -||-   ---  Capacitance diode (Varicap) ref:C10
               / \
                |   75ohms
(GND)---------------/\/\/--- Vcc

        
16.     Power Supply
        ------------

               +4.5V -----SSSSS-------------------------,
                      :   Self?   |      |               \|         PNP
                      :   (R=0)   |      |                |---   Transistor
                    ,---'        \ /    \ /              /|   |    ref:YB51
            Zener    / \         ---    ---       x4 -->'     |     or YB58
           ref:Z3N    :           |      |                    |  
         omitted on   :           |      |-- Vcc(10)          | 
        recent PCB's  :          x3      |                    |
                      :                 XXX  Capa?            |
                      :                 ???  ref:336          |
                      :                 ???      16k          |
                      :                  |       429          |
                       ' ' ' ' ' ' ' ' ' |--------------------
                                       --|--
                                        -|-
                                         -

17.     Backup Power Supply
        -------------------

                          +| |               | |
                Vcc -------| |---------------| |-------- Vcc(on)
                           | |       |       | |
                           1mF       |      0.1uF
                                   --|--
                                    -|-
                                     -
18.     Miscellaneous
        -------------

18.1
 When a current larger than ~120mA flows through the CPU,
 all the indicators will be set independantly of the HP state.


19.     Contacting the author
        ---------------------

        Philippe TEUWEN
        Belgium
        s952365@student.ulg.ac.be
