Texas Instruments TMC0501 Arithmetic Chip

• Features

Texas Instruments introduced on January 15, 1974 with the SR-50 their first "Slide Rule" calculator adding trigonometric and hyperbolic functions to the feature set of the SR-10, SR-11, and SR-16 line of calculators to compete with Hewlett Packard’s HP-35. The SR-50 was the first product based on the TMS0500 Building Blocks for Scientific and Programmable Calculators and used its minimum configuration combining the TMC0501 Arithmetic Chip and one TMC0521 SCOM (Scanning Read-Only Memory) Chip with the necessary display drivers for its 14-digit LED display, power supply and clock generation. Later Scientific Calculators made use of the flexibility of the TMS0500 architecture by using multiple SCOMs (SR-51), adding program and data memory (SR-56) and even magnetic card readers (SR-52) and a printer and matrix display (SR-60).

All TI scientific and programmable calculators introduced between 1974 (SR-50) and 1976 (SR-56) and the high-end models between 1977 (TI-59) and 1979 (TI-58C) adopted the TMS0500 Building Blocks for Scientific and Programmable calculators:

• TMC0501 Arithmetic Chip – Register Processor with five 16-digit Registers and segment decoder/driver
• TMC0501E Enhanced Arithmetic Chip – Optimized for AOS
• TMC0520 Scanning and Read-Only Memory Chip – 1,024*13 Bits Instruction Memory with serial interface to Arithmetic Chip, 16 Constants with 16 digits, each and 16-digit display scanning
• TMC0530 Scanning and Read-Only Memory Chip – TMC0520 with integrated clock oscillator
• TMC0540 Customer Read-Only Memory Chip – 5,000*8 Bits Keycode Memory for Solid State Software Modules
• TMC0560 Bare Read-Only Memory – 1k*13 Bits Instruction Memory with serial interface to Arithmetic Chip, 8-pin package
• TMC0580 Double Scanning and Read-Only Memory Chip – 2.5k*13 Bits Instruction Memory with serial interface to Arithmetic Chip, 16 Constants with 16 digits, each and 16-digit display scanning
• TMC0590 Continuous Memory Interface Chip – Adopts 1k*4 Bits CMOS SRAM with backup battery to Arithmetic Chip
• TMC0594 Magnetic I/O Chip – Four channel interface for magnetic card reader – TI-59
• TMC0595 Magnetic I/O Chip – Four channel interface for magnetic card reader – SR-52
• TMC0596 Magnetic I/O Chip – Four channel interface for magnetic card reader – SR-60
• TMC0598 Multi-Register Chip – TMC0599 with single-voltage supply
• TMC0599 Multi-Register Chip – 240*8 Bits Random Access Memory with 4-bit I/O Bus to Arithmetic Chip, stores 240 program steps or 30 numbers of 16 digits, each

The TMS0500 Building Blocks are an evolution of the TMS0200 Building Blocks for Desktop Calculators introduced already in 1973 with the TI-4000 and clearly designed with portable calculators in mind, consequently minimizing the necessary real estate of the "calculator brain":

• TMS0200 - Minimum configuration: 40-pin Data Chip + 40-pin ROM Chip + 16-pin Segment Decoder, optional ROM Expansion with 40-pin ROM/Register Chip
• TMS0500 - Minimum configuration: 28-pin Arithmetic Chip + 28-pin Scanning ROM Chip, optional ROM Expansion with piggy-backing a second Scanning ROM Chip and/or additional 8-pin Bare ROM Chips

The TMS0200 is based on the Register Architecture of the TMS0100 single-chip calculator circuit design introduced in September 1971 but expands its Serial-Access Memory (SAM) from 3 Registers * 13 digits to 4 Registers * 16 digits, outsources the 320*11 Bits Program Memory and display scanning to a TMS0300 ROM Chip with a capacity of 512*13 Bits and 13 digits scan outputs and abandons the integrated segment decoder.

The TMS0500 optimized the TMS0200 Register Architecture for Desktop Calculators with expanding its SAM from 4 Registers to 5 Registers * 16 digits, using a 10 Digits Mantissa and 2 Digits Exponent representation and doubling the Programming Memory from 512*13 Bits to 1,024*13 Bits. The task sharing between Data Chip and ROM Chip of the TMS0200 was slightly changed and the TMC0501 Arithmetic Chip does not include any keyboard or display scanning, the TMC0520 SCOM (Scanning and Read-Only Memory) Chip features a total of 16 digit outputs in addition to the 16 stored constants used with transcendental functions with 16 digits, each. In addition to the 5 Registers of the TMC0501 Arithmetic Chip labeled A, B, C, D, and E integrates the SCOM Chip two additional Registers with 16 digits capacity each, and named accordingly Register F and Register G .

Communication between the TMC0501/TMC0501E Arithmetic Chips to the other family members of the TMS0500 Building Blocks is realized with multiple means:

• IDLE, PHI 1 and PHI 2 Signals are used to synchronize all peripherals connected to the TMC0501/TMC0501E Arithmetic Chips with the 16 States of its Instruction Cycle
• EXT Output indicates that the TMC0501/TMC0501E Arithmetic Chips is addressing external memories/registers
• EXT Input to receive 2-digit BCD Keycodes (8-bit) from the TMC0540 CROM Chips
• IRG Input to receive the 13-bit Instruction Words from the TMC0520/TMC0530/TMC0560/TMC0580 ROM Chips
• 4-bit bidirectional I/O Bus I/O 8, I/O 4, I/O 2, and I/O 1 to communicate with Multi-Register Chips and other peripherals
• Various Condition and Flag Outputs to signal certain states of operations to its peripherals
• BUSY Input for slow devices like the Printer Chip

The TMC0501 was soon replaced with the TMC0501E and only early products make us of the original design.

QUICK-LINK to TMS0500 Family.

• Applications

SR-50, SR-50A, SR-51, SR-51A, SR-52, SR-56, SR-60

• Revisions

Revision Products First Prototypes Comments
TMC0501 SR-50   Initial design
TMC0501 Rev A SR-50    
TMC0501 Rev B SR-50    
TMC0501 Rev C SR-50   Marking C and/or -4
TMC0501 Rev D SR-50, SR-51 October 1974 Marking D and/or -5, -6
TMC0501 Rev E SR-52 April 1975 Marking E and/or -5
Renamed to TMC0501E

Lacking "backward compatibility" between the individual Revisions of the TMC0501 Arithmetic Chip and products using AOS relying on the Rev E of the design, Texas Instruments consequently renamed the TMC0501 Rev. E  into TMC0501E Enhanced Arithmetic Chip.

• Architecture

  Description Comments
Architecture Building Blocks Arithmetic Chip
Category Register Processor 64-bit registers (16 digits * 4 Bits)
ROM Size not applicable 13-bit wide (8k*13 Bits) Memory Addressing
RAM Size 320 Bits 5 Registers * 64 Bits

• Technical Specifications

Parameter Min Typ Max Unit Comments
VSS   0   V  
VDD -10.5 -10.0 -9.5 V  
VGG -16.3 -15.8 -15.3 V  
PHI1, PHI2   225 230 kHz Opposite phases

• Technology

The TMC0501 was manufactured in a 8 um metal gate PMOS process (metal width = 0.3 mil / 8.0 um, metal spacing = 0.30 mil / 8.0 um, diffusion width = 0.25 mil / 6.0 um, diffusion spacing = 0.35 mil / 9.0 um).
The die size of the TMC0501 is approximately 215 mils * 220 mils / 5.5 mm * 5.6 mm.

• Packaging

The TMC0501 uses a standard 0.6” wide 28-pin DIP (Dual In-line Package with a 0.1” / 2.54 mm lead pitch).

• Pin Configuration

Pin IO Function Pin IO Function
1 O Segment driver DP 28 O Segment driver G
2 O Segment driver B 27 V Negative Voltage VGG
3 O Segment driver A 26 V Negative Voltage VDD
4 O Segment driver F 25 IO SCOM Interface D0
5 O Segment driver C 24 IO SCOM Interface D1
6 O Segment driver D 23 IO SCOM Interface D2
7 O Segment driver E 22 IO SCOM Interface D3
8 I Keymatrix input T 21 I Instruction words
9 I Keymatrix input S 20 O Calculating status
10 I Keymatrix input R 19 O External access
11 I Keymatrix input Q 18 I Clock Input 2
12 I Keymatrix input P 17 I Clock Input 1
13 I Keymatrix input O 16 V Common Voltage
14 I Keymatrix input N 15 O Segment driver H
The Segment drivers A-G and DP (Decimal Point) are connected to the display in the pictured way. The H segment is used for the negative sign of the Mantissa and computing symbol. 

• Keyboard Scan-Matrix

The keyboards of all calculators based on the TMC0501 Arithmetic chip consist of a x/y-matrix connected to the SCOM digit driver outputs and the TMC0501 keymatrix inputs. Find the corresponding key connection within the SCOM datasheets.

• Display

Calculators based on the TMC0501 make use of a 14-digit LED (Light-Emitting-Diode) Display with common cathode architecture. Early calculators like the SR-50 or SR-51 use 14 TILxxx modules, later models like SR-50A or SR-56 use the LED-stick 234. The segments are driven directly from the TMC0501, the digits use external drivers (SN27882) connected to the corresponding SCOM chip. 

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If you have additions to the above datasheet please email:

© Joerg Woerner, February 02, 2001. No reprints without written permission.