Texas Instruments TMC0501E


With the TMC05xx building blocks Texas Instruments created a novel architecture for scalable scientific calculators. The architecture uses minimum a 2 chip design with the Arithmetic chip TMC0501E and the SCOM (Scanning Read Only Memory) but was expandable to a maximum of 8 SCOMs, additional RAM as program memory for programmable calculators, additional RAM for general purpose registers and even a chip driving a printer. Most scientific and programmable calculators from Texas Instruments between the years 1974 and 1982 (SR-50..TI-59) use these chips.

The TMC0501E Arithmetic chip contains a decimal ALU (Arithmetic and Logic Unit) with a accuracy of 13 digits. Each result is represented in 16 digits, 13 digits for the mantissa, 2 digits for the exponent and one digit for the signs and overflow bits. There are in total 5 registers of 16 digits for storage purposes.

Additional functions of the TMC0501E include the segment outputs of the display and the keyboard scanning input. Both the scanning of the display digits and the keyboard is done by the SCOM companion chip.

The differences between the TMC0501 and the TMC0501E are at the moment not confirmed but most likely related to the AOS (Advanced Operating System) used with the TI-59 and related calculators.

Family Members and Applications

SR-60A, TI-58, TI-59

Technical Specifications

Item 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


The TMC0501E uses a 0.4 wide 28-pin SPDIP (Shrink Plastic Dual In-line Package with a 0.07 / 1.778 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 the Decimal point are connected to a display in the pictured way. The H segment is used for the leading sign and computing symbol.

Keyboard Scan-Matrix

The keyboards of all calculators based on the TMC0501E Arithmetic chip consist of a x/y-matrix connected to the SCOM digit driver outputs and the TMC0501E keymatrix inputs. Find the corresponding key connection within the SCOM datasheets.


Calculators based on the TMC0501E make use of a 12-digit LED-display with common cathode architecture. The TI-58 and TI-59 use the LED-stick xxx. The segments are driven directly from the TMC0501E, the digits use external drivers (SN27882) connected to the corresponding DSCOM 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.