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HP 65 Internals

Posted by Tony Duell (UK) on 18 Sept 2003, 9:22 p.m.

There are 3 PCBs in the case. The lowest one contains the keyboard 
switches, displays, and display drivers. It connects by a 28 pin 
connector to the logic PCB, which contains the PSU, CPU hybrid and ROMs. 
The logic PCB is then connected to the card reader PCB by a 10 pin 
connector. The card reader head and motor are hardwired to the card 
reader PCB.

The 28 pin connector between the keyboard/display and the logic PCB carries similar signals to the 25 pin connector in the HP35, together with 3 switch signals from the card reader contacts and the program switch signal. The pinout is :

1 (LHS of machine) o-- Disp 0 o-- Disp 1 o-- Disp 2 o-- KC1 o-- Disp 3 o-- Disp 4 o-- HDS/ o-- WPS o-- MTRS/ o-- Phi_1 o-- KC2 o-- Vbsw o-- Phi_2 o-- Gnd o-- Vcc o-- PGMSw/ o-- KC3 o-- KR1 o-- KR2 o-- KR3 o-- KC5 o-- KR4 o-- KC4 o-- KR5 o-- KR6 o-- KR7 o-- KR8 o-- RCD

KC = keybaord column line, KR = keyboard row line Disp = display data bus from CPU hybrid to anode driver RCD = Reset cathode driver (start display scan) Phi_n = 2 phase clock from anode driver to CPU Vcc = 8.2V power line to cathode driver Vbsw = Switched battery voltage PGMSw/ = program mode switch (ground = w/pgm mode) HDS/ = card reader head swtich (ground = card over head) MTRS/ = card reader motor switch (ground = card inserted) WPS = card reader write protect switch (ground when HDS/ goes to ground = corner not clipped)

There are 2 custom chips on the keyboard/display PCB :

1820-1029 (anode driver and system clock)

---------- Disp0 --| U |-- Ag Disp1 --| |-- Ae Disp2 --| |-- Ah Disp3 --| |-- Af Disp4 --| |-- Ad Step --| |-- Gnd Phi_1 --| |-- Ab Phi_2 --| |-- Ac LC --| |-- Aa Rset --| |-- Vbsw ----------

Disp = Display data bus (as above). A = display anode drive lines [1], segments named conventionally (h = decimal point) Phi_n = clock output to logic board Step = step output to cathode driver (display scanning) LC = oscillator components (LC series circuit from here to ground) Rset = resistor from here to ground, appears to be part of low battery circuit

[1] There's an inductor of 130uH (or 68uH for the point) from each anode line to Vbsw. Display runs from back-emf from these inductors. The HP65 uses 4-inductor hybrid modules rather than the discrete inductors used in earlier machines :

1810-0146

Ae---UUUUU---+ 130uH | | Af---UUUUU---+ 130uH | | Ah---UUUUU---+ 68uH | | Ag---UUUUU---+ 130uH | | Vbsw---------+ C

1810-0147

Aa---UUUUU---+ 130uH | | Ab---UUUUU---+ 130uH | | Ac---UUUUU---+ 130uH | | Ad---UUUUU---+ 130uH | | Vbsw---------+ C

1820-1226 cathode driver (essentially a 15 stage shift register for display scanning).

---------- k9 --| U |-- k8 k10 --| |-- k7 k11 --| |-- k9 Vbsw --| |-- k5 k12 --| |-- k4 k13 --| |-- Vbsw k14 --| |-- k3 RCD --| |-- k2 Step --| |-- k1 Vcc --| |-- k15 ----------

k = display cathode outputs. Step = display scan clock from anode driver RCD = Reset Cathode Driver = start scan (from A&R chip) Note lack of ground pin -- runs between Vcc (8.2V) and Vbsw (4V).

Logic PCB --------- The discrete components on this board are almost all part of the PSU, which is very similar to that in earlier machines. It provides Vss (+6.25V) and Vgg (-12V) to the logic, and Vcc (+8.2V) to the display driver.

The CPU in this machines is a 44 pin hybrid circuit containing 6 chips. These are believed to be :

Arithmetic and Registers Control and Timing 2 * RAM (data and user program store?) Clock driver and init Card Reader Controller.

The pinout of the hybrid (60218-00065) is :

-------------- WE --| U |-- RB WPS --| |-- RA T/P --| |-- HDS/ --| |-- Phi_2 In MTRS/ --| |-- Phi_1 In WB --| |-- Phi_2 Out WA --| |-- Phi_1 Out IA --| |-- Init Gnd --| |-- Init C Vss --| |-- Data Disp2 --| |-- RCD Disp1 --| |-- IS Disp0 --| |-- Sync Disp3 --| |-- PGMSw/ Disp4 --| |-- WS Vgg --| |-- KC1 KR2 --| |-- KC2 KR3 --| |-- KC3 KR4 --| |-- KC4 KR5 --| |-- KC5 KR6 --| |-- KR7 KR1 --| |-- KR8 --------------

KR = Keyboard row lines, KC = keyboard column lines Disp = display data (to anode driver) RCD = Reset Cathode Driver Phi_n In = 2 phase clock input from anode driver Phi_n Out = 2 phase clock output to ROMs Init C = Reset capacitor input (2.2uF from this pin to ground) Init = Reset output to ROMs Sync = machine cycle synchronisation IA = Instruction Address to ROMs IS = Instruction from ROMs WS = Word select Data = serial BCD data from X register (testpoint) Vss = +6.25V, Vgg=-12V power lines PGMSw/ = program switch input HDS/, MTRS/, WPS = card reader switch inputs (see above) RA, RB = Read data inputs from the 2 card reader tracks WA, WB = Write data outputs to card reader tracks WE = Card reader write enable T/P = testpoint (connected to card reader connector)

The other 3 chips on the logic PCB are ROMs :

1818-0073, 1818-0074, 1818-0075

------- Vss --| U |-- --| |-- IA --| |-- WS Gnd --| |-- Init --| |-- Phi_1 IS --| |-- Vgg Sync --| |-- Phi_2 --| |-- -------

The signals are as described above.

There are 10 testpoints on the logic PCB :

(Top of machine) o-- Sync o-- IS o-- IA o-- Vgg o-- Phi_2 Out o-- Phi_1 Out o-- Init o-- Data o-- WS o-- RCD

There is also a 10 pin connector to the card reader :

(Top of machine) o-- Vss o-- RA o-- RB o-- WE o-- T/P (from CPU pin 3) o-- WB o-- WA o-- Vbsw o-- MTRS/ o-- Gnd

RA, RB = Read data from card reader to CPU (2 tracks) WA, WB = Write data from CPU to card reader (2 tracks) WE = Write Enable Vbsw = switched battery voltage Vss = +6.25V MTRS/ = motor switch (to start card reader motor)

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

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

1826-0158

----------- 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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