Texas Instruments PC-100 Printer Cradle

Date of introduction:  September 16, 1975 Display technology:  
New price:  $295.00 (SRP 1976) Display size:  
Size:  10.4" x 11.3" x 4.1" Printer technology:  Thermal TP-30250
Weight:  5 pounds 9 ounces Serial No:  013104
Batteries:   Date of manufacture:  week 17 year 1976
AC-Adapter:   Origin of manufacture:  USA (LTA)
Precision:   Integrated circuits:  TMC0251, TMC0561, TMC0569, 4*SN96912
Program steps:   Courtesy of:  Joerg Woerner
Download leaflet:   (US: 7.8M Bytes)
  (US: 3.5M Bytes)

The PC-100 Printer Cradle was introduced together with the SR-52. Its thermal printer has 64 alphabetic, numeric and special characters which can be printed at the rate of 60 characters per second. Up to 20 characters can be printed per line on 2.5 inch wide thermal paper.

The PC-100 can also be used to print, list or trace program steps as an aid to debugging. 

The PC-100 Printer Cradle in addition offers some extra features: It functions as a power-adapter and also has a storage/charging compartment where you can charge the battery pack. The calculator (and battery pack compartment) is locked solidly to the Printer Cradle with the use of a key.

PC-100_2.jpg (10838 Byte)The PC-100 sports a switch that makes it compatible with both the SR-52 and SR-56.

The featured PC-100 with Date code LTA 1776 was manufactured in April 1976 by Texas Instruments in their Lubbock, TX facility. Dismantling the unit reveals a design centered around a mix of the TMS0200 Building Blocks introduced in 1972 with the Canon Canola 121F and the TMS0500 Building Blocks introduced in January 1974 with the legendary SR-50 Scientific calculator.

Main components of the electronics of the PC-100 are a TMC0251 Printer/Display Chip that can interface to both a Thermal Printer Mechanism or a Dot-Matrix Display and two TMC0561 and TMC0569 Bare Read-Only Memory (BROM) Chips holding the firmware for the SR-52 respective SR-56 calculators. The previously mentioned switch to select between the two calculators actually connects one of the two "IRG" Pins of the BROMs to the TMC0501E Enhanced Arithmetic Chip of the attached calculator.

The other Integrated Circuits on the Main printed circuits board (PCB) are a TP4050AN Buffer Chip for the two CLK signals of the TMC0501E architecture and four SN96912N Driver Chips with six channels, each. Twenty of the channels are used for the thermal print head and the remaining four channels are used for its stepper motor.

A second PCB is wired with a flat ribbon cable to the Main PCB and with two connectors to the docking connector and switches of the Printer Cradle. It carries the electronics for the power supply of the PC-100 Printer Cradle and three additional diodes for the key matrix inputs of the TMC0501E Chip.

And last but not least holds a small third PCB the [PRINT], [TRACE], [ADV] switches and the Power LED.

Note: We removed the large heat sink of the TIP30 power transistor (residual of the thermal paste still visible), the large power transistor mounted upside down is a TIP120 when we prepared our TMC0500 Platform to record the ROM Image of the TMC0561 and TMC0569 BROMs. Comparing the Instruction ROM Content of the TMC0561 used with the SR-52 and the TMC0569 used with the SR-56 shows as expected many differences.

The 12-pin docking connector uses 11 signals to communicate between the SR-52 or SR-56 calculator and the PC-100 Printer Cradle:

Pin 1: KR (Key matrix input KR of TMC0501E) - Connected to BUSY output of TMC0251
Pin 2: KP (Key matrix input KP of TMC0501E) - D0 PC-100 Present, D12 [PRINT] switch, D15 [TRACE] switch
Pin 3: KN (Key matrix input KN of TMC0501E) - D12 [ADV] switch
Pin 4: CLK 1 of TMC0500 Building Blocks
Pin 5: Digit Times Output D0 - PC-100 Present with KP
Pin 6: Digit Times Output D15 - [TRACE] switch KP
Pin 7: IRG (Instruction Words) of TMC0500 Building Blocks
Pin 8: IDLE (State and Digit Synchronization) of TMC0500 Building Blocks
Pin 9: EXT (External memory Access) of TMC0500 Building Blocks
Pin 10: CLK 1 of TMC0500 Building Blocks
Pin 11: Digit Times Output D12 - [ADV] switch KN and [PRINT] switch with KP
Pin 12: N/A (left most pin on printer cradle connector)

The use of the Digit Times Output signal D0 to allow a connected calculator to detect presence or absence of the PC-100 is actually a show stopper for the SR-50A (Version 2) calculator, its revised electronics doesn't support scanning D0 like the SR-51A (Version 2) and the SR-56. Learn more about Printing with the SR-51 / SR-51A

With the introduction of the TI-58 and TI-59 the PC-100 was replaced with the PC-100A.

The PC-100 is featured in the Texas Instruments Incorporated bulletins CB-195A and SR-52_FL dated 1976 and in the Texas Instruments Deutschland GmbH leaflet ER-1976 dated 1976.


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If you have additions to the above article please email:

Joerg Woerner, September 25, 2002. No reprints without written permission.