Texas Instruments TMS0300 ROM Chip


Texas Instruments introduced in 1973 with the TI-4000 Desktop calculator a very compact, yet capable product with a 12-digit display as an upgrade option to the TI-3000 and TI-3500 calculators with 8-digit resp. 10-digit displays. The TI-4000 was one of the first applications of TIs TMS0200 Building Blocks for Desktop Calculators, a groundbreaking architecture centered around a Data Chip and various Support ICs:

TMS0200 Data Chip Register Processor with four 16-digit Registers and seven Keyboard Scan inputs
TMS0300 ROM Chip 512*13 Bits Instruction Memory with serial interface to Data Chip and 13-digit display and keyboard scanning, up to 4 ROM Chips
TMC0400 ROM/Register Chip - 512*13 Bits Instruction Memory with parallel interface to ROM Chip and two 16-digit Registers
TMS0220 Printer Chip Interface to two-color Drum Printer Mechanism
TMC0250 Printer/Display Chip Interface to Thermal Printer Mechanism and Dot-Matrix Display

The TMS0200 Data Chip requires in a minimum configuration as used in the TI-4000 a TMS0300 ROM Chip for Program Memory and to scan up to 13 digits of the display.

The TMS0300 combines two Building Blocks of a 12-digit Desktop Calculator in one 40-pin package:

Instruction Memory for the Data Chip with a capacity of 512*13 Bits
Scanning of the Display and Keyboard

The combination of both its programmability and scalability of the TMS0200 Building Blocks for Desktop Calculators allowed the introduction of some interesting products like the Hexadecimal Calculator/Converter SR-22 bypassing the BCD correction of the ALU (Arithmetic Logic Unit) or the massive Printing Desktop calculator TI-620

The 13-bit wide Instructions Words of the TMS0200 Data Chip are divided into two chunks of 6 bits and 7 bits and transmitted through two serial output pins to the corresponding pins of the (IRG A B0 B5) and IRG B B6 B12) to allow for a faster transfer than using a single serial data port while still saving many connection pins compared to a parallel transfer of the data.

A parallel interface with 13 inputs allows for the connection of a TMC0400 ROM/Register Chip for an expansion of the ROM capacity by an additional 512*13 Bits.

Display and Keyboard scanning for up to 15 digits is shared between the TMS0300 ROM Chip (11 digits D2 D12) and TMS0200 Data Chip (4 digits D1, D13 D15), synchronization between the devices is accomplished with four 4 S-Times Outputs SA, SB, SC, and SD generated by the TMS0200 Data Chip to signal the 16 States of its Instruction Cycle. The TMS0200 sports seven inputs for the keyboard matrix allowing up to a maximum of up to 105 keys and/or switches.

While none of the known products based on the TMS0200 Building Blocks makes fully use of their possibilities like addressing up to 4 ROM chips and up to 16 Register Chips, did the design lay out the architecture of the TMS0500 Building Blocks for Scientific Calculators introduced with the "Slide Rule" calculator SR-50 in January 1974 and leading all the way to the legendary TI Programmable 59 and the amazing SR-60A Prompting Desktop calculator.

With each product based on the TMS0200 Building Blocks for Desktop Calculators using at least one TMS0300 ROM Chip and Texas Instruments numbering them in a sequential way, we can easily track the individual designs.

QUICK-LINK to TMS0200 Family.

Products and Applications

Only certain Desktop and Scientific Calculators introduced between 1973 and 1974 by Texas Instruments, Canon, Olympia and Teal adopted the TMS0200 Architecture, while the TMC0250 Printer/Display Chip found its way into the wildly successful PC-100 Printer Cradle for the SR-51, SR-52, SR-56, TI-58, TI-58C, and TI-59 calculators and the SR-60 Prompting Calculator.

Family Members and Applications

Type Calculators Function
TMS0301 TI-4000, TI-410 [+=] [-=] keys, Memory, K
Panaplex Display
TMS0302 Canon L121F [+=] [-=] keys, Memory, K
Panaplex Display
TMS0304 SR-20 [+] [-] [=] keys, x2,1/x, sqr(x), x!, PI, ex
Panaplex Display
TMS0305 TI-500 [+=] [-=] keys, Memory, K
Printer only
TMS0306 TI-620 [+=] [-=] keys, 2 Memories, K
Printer only. Uses TMC0406
TMS0311 TEAL PM1200 [+=] [-=] keys, Memory, K
Panaplex Display
TMS0318 Olympia CD401A [+=] [-=] keys, Memory, K, %
TMS0320 TEAL 6121D, Elite 1202M [+=] [-=] keys, Memory, EX, K, %, sqr(x)
TMC0321 Canon L1210 [+=] [-=] keys, Memory, K, %, sqr(x)
Panaplex Display
TMC0322 TI-450 [+=] [-=] keys, Memory, K
Panaplex Display
TMC0323 SR-22 Hexadecimal Calculator/Converter
Panaplex Display. Uses TMC0404

Note: Learn more about the MOS Numbering System used by Texas Instruments' early MOS Chips.

Technical Specifications

Parameter Min Typ Max Unit Comments
VSS +9.2 +10.0 +10.6 V  
VDD   0   V  
VGG -7.2 -7.0 -6.4 V  
PHI1, PHI2 50 250 300 kHz Opposite phases


The TMS0300 was manufactured in a metal gate PMOS process.


The TMS0300 uses a 0.6 wide 40-pin DIP (Dual In-line Package with a 0.1 / 2.54 mm lead pitch).

Pin Configuration

Pin IO Function Pin IO Function
1 V VSS (+10 V) 40 I Clock Input 1
2 O Instruction word B0-B5 39 I Clock Input 2
3 O Instruction word B6-B12 38 V VGG (-7 V)
4 I Expansion ROM Instr. B0 37 V VDD (0 V)
5 I Expansion ROM Instr. B1 36 O Digit driver 2
6 I Expansion ROM Instr. B2 35   Digit driver 3
7 I Expansion ROM Instr. B3 34 O Digit driver 4
8 I Expansion ROM Instr. B4 33 O Digit driver 5
9 I Expansion ROM Instr. B5 32 O Digit driver 6
10 I Expansion ROM Instr. B6 31 O Digit driver 7
11 I Expansion ROM Instr. B7 30 O Digit driver 8
12 I Expansion ROM Instr. B8 29 O Digit driver 9
13 I Expansion ROM Instr. B9 28 O Digit driver 10
14 I Expansion ROM Instr. B10 27 O Digit driver 11
15 I Expansion ROM Instr. B11 26 O Digit driver 12
16 I Expansion ROM Instr. B12 25 I Strobe
17 I Condition Flag 24 I S-Times D
18 I P Register 23 I S-Times C
19 I Condition Flag A 22 I S-Times B
20 I Condition Flag B 21 I S-Times A

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If you have additions to the above datasheet please email:

Joerg Woerner, March 7, 2021. No reprints without written permission.