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HP 67 Internals

Posted by Tony Duell on 2 Oct 2003, 9:42 p.m.

This machine may look like a 'classic series', but it uses an ACT 
(Arithmetic, Control, Timing) processor chip, and is electrically a 
Woodstock.

There are 3 PCBs in the case. The uppermost one (with the machine in the normal operating position) carries the keyboard, display, display drivers and card reader switch contacts. This is connected by 28 pins to the logic PCB that contains the processor, memory, card reader controller and power converter. Finally, this is connected bu a 10 pin connector to the card reader PCB (very similar to that in the HP65).

Connections from Keyboard to Logic PCB :

LHS of machine o-- Vbsw o-- Vbsw o-- PGMSw/ o-- Phi_1 o-- Sync o-- ISA o-- KC1 o-- KC2 o-- KC3 o-- KC4 o-- KC5 o-- HDS/ o-- MTRS/ o-- RCD o-- WPS o-- STR o-- SF o-- SA o-- SB o-- SC o-- SD o-- SG o-- SE o-- SH o-- Idisp o-- Ibias o-- Gnd o-- Gnd

Vbsw : Switched Battery voltage, Gnd : Ground PGMSw/ : Program/Run switch (low = Program mode) Phi_1, Sync, ISA : Logic PCB testpoints (not connected on keyboard) KCn : Keyboard column lines HDS/ : Card at reader head MTRS/ : Card reader motor swtich WPS : Card reader write protect (corner clipped) switch RCD : Reset cathode driver, STR : Display digit strobe Sx : Display segment drive lines Idisp : Display current control, Ibias : control resistor

The keyboard PCB contains 2 ICs :

1820-1749 Cathode driver (also scans keyboard rows): Essentially a shift register to select the kn lines in turn.

----------- k3 --| U |-- k2 k4 --| |-- k1 k5 --| |-- STR k6 --| |-- RCD k7 --| |-- Vcc k8 --| |-- BT k9 --| |-- LLD k10 --| |-- k14 k11 --| |-- k13 Gnd --| |-- k12 -----------

kn = Display carhode lines Vcc = Switched battery voltage RCD = reset cathode driver STB = digit strobe BT = Low battery control input LLD = Low batter LED drive output

1858-0050 = CA3082 NPN transistor array Yes, a standard IC in an HP handheld. It has 7 NPN transistors with a common collector (to the IDisp line). These drive the following segments: Section Segment a b b e c c d f e a f h (decimal point) g d

The g segment is driven by one of the discrete NPN transistors on the keyboard PCB, the other 3 transsitors form a circuit to map both minus signs (g segments of figts 3 and 15) into the same digit. Note that the display is 'both ways scanned' -- a digit is selected, then the segments for that digit position are selected in turn.

The keyboard is scanned by the cathode driver, 8 of the outputs select rows of the keyboard

Keyboard row Cathode line 1 8 2 6 3 13 4 5 5 11 6 3 7 9 8 7

Logic PCB ---------

Two of the discrete transsitors here form the standard HP power converter circuit giving Vcc (+6.2V) and Vgg (-12V) from the battery. The other 2 form a current mirrr circuit to set the display current.

1820-2530 : ACT processor

----------- Vss---| U |-- Vgg --| |-- RCD F1 --| |-- Sync F2 --| |-- PWO/ KC1 --| |-- POR KC2 --| |-- Phi_1 KC3 --| |-- Phi_2 KC4 --| |-- KC5 --| |-- LC1 ISA --| |-- LC2 Data --| |-- Gnd -----------

Vss : +6.2V, Vgg : =12V F1, F2 : Flag inputs (F1 N/C, F2 from card reader controller FLG line) KCn : Keyboard columns ISA : Instruction and Address signal to/from memory Data : Data line for RAM devices Sync : Bus sync line (Low during instruction part of the cycle, most of the time) Phi_n : 2 phase system clock (outputs on CPU) LCn : Connections for parallel LC clock tank circuit PWO/ : Power off POR : Power On Reset (conencted to Vss via 2.2uF capactior)

1818-0268 : ROM 0 and display decoder

--------- SA --| U |-- Sync SF --| |-- Vgg SB --| |-- Phi_2 SC --| |-- Phi_1 I --| |-- SD --| |-- ISA SH --| |-- Gnd SE --| |-- STR SG --| |-- Vss --------- Vss, Vgg : Power supply ISA : Instruction and Address Sync : System bus sync input Phi_n : 2 phase system clock STR : Display digit strobe Sx : Segment drive outputs (to display anode driver) I : Display current control input (connected to Vxx via resistor)

1818-0550, 1881-0551, 1818-0231, 1818-0232 ROM/RAM ICs

----------- Vss--| U |-- Sync Phi_2 --| |-- ISA Vgg --| |-- Gnd Phi_1 --| |-- Data ----------- Vss, Vgg : Power supply ISA : Instruction and Address Sync : System bus sync input Phi_n : 2 phase system clock

Each chip contains ROM and 16 7 byte registers, so a total of 64 registers in the machine. 32 of them are used for 32*7 = 224 bytes (steps) of user program memory). The other 32 registers form the 26 user register (P0-P9, S0-S9, A-E and i), the 5 stack registers and one register containing the user flags, angle mode, decimal setting, etc.

1820-1751 Card Reader Controller ----------- Motor/ --| U |-- Gnd Vss --| |-- Flg/ WPS --| |-- MTRS/ --| |-- HDS/ --| |-- PWO/ --| |-- SF1 RB --| |-- RA --| |-- WE --| |-- WA --| |-- WB --| |-- Data --| |-- ISA Phi_1 --| |-- Sync Phi_2 --| |-- Vgg -----------

Vss, Vgg : Power supply ISA : Instruction and Address Sync : System bus sync input Phi_n : 2 phase system clock PWO/ : Power off HDS/ : Card at reader head MTRS/ : Card reader motor swtich WPS : Card reader write protect (corner clipped) switch SF1/ : Flag input (from Program switch) FLG/ : Flag output (to ACT F2) RA, RB : Card read data WA, WB : Card write data WE : Card write enable Motor/ : Motor on

Card reader to logic PCB connector :

Top of machine :

o-- Vss o-- RA o-- RB o-- WE o-- o-- WB o-- WA o-- VBsw o-- Motor/ o-- Gnd

Vss, VBsw, Gnd : Power supply RA, RB : Card read data WA, WB : Card write data WE : Card write enable Motor/ : Motor on

Card reader -----------

The 20 pin IC on the card reader PCB is the sense amplifier, write driver and motor controller. The pinout is :

1826-0322

----------- Vm --| U |-- Vbb TR --| |-- Vss GB --| |-- Vbsw HAC --| |-- MTRS/ HA --| |-- MI (connected to Vbsw) CA --| |-- WA Gnd --| |-- RA HBC --| |-- WB HB --| |-- RB CB --| |-- WE -----------

Vm = Motor voltage output TR = Motor speed control resistor (other end to Vm) GB = Motor ground (to -ve side of battery pack and motor) Vbb = Unswitched battery voltage Vbsw = Switched battery voltage Vss = +6.25V power input MTRS/ = Motor run input WA, WB = Write data inputs RA, RB = Read data outputs WE = Write Enable input HA, HB = one side of head winding (for each track) CA, CB = +ve end of 22uF cap (other side to HAC, HBC) HAC, HBC = -ve side of 22uF cap, other end of head winding.

Head wiring colours :

Blue = HA ) Track A winding Orange = HAC )

Red = HB ) Track B winding Yellow = HBC )

Black = ground

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