Texas Instruments TMC0400 ROM/Register 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 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 TMC0400 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 as an extension of the 512*13 Bits of the TMS0300 ROM Chip
Two 16-bit Data Registers "E" and "F" as an extension of the four Data Registers "A", "B", "C", and "D" of the TMS0200 Data Chip

Prerequisite for the use of the TMC0400 ROM/Register Chip is at least a combination of a TMS0200 Data Chip and TMS0300 ROM Chip due to the parallel data output of the additional 13-bit Instruction Words. The TMS0300 receives the 13-bit Instructions from the TMC0400 through 13 parallel inputs I0 I12 and transmits them serially in two chunks of 6 bits (IRG A B0 B5) and 7 bits (IRG B B6 B12) to the TMS0200 Data Chip.

Access to the two 16-bit Data Registers of the TMC0400 ROM/Register Chip is realized through a 4-bit bidirectional I/O Bus with the TMS0200 signalizing the 16 States of the Instruction Cycle through the S-Times Outputs SA, SB, SC, and SD.

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 TMC0500 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 only a few designs based on the TMS0200 Building Blocks for Desktop Calculators using the optional TMC0400 ROM/Register 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
TMC0404 SR-22 Hexadecimal Calculator/Converter
Panaplex Display. Uses TMC0323
TMC0406 TI-620 [+=] [-=] keys, 2 Memories, K
Printer only. Uses TMS0306

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 TMC0400 is manufactured in a tbd um metal gate PMOS process.


The TMC0400 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 IO I/O Bus I/O 4 40 IO I/O Bus I/O 1
2 IO I/O Bus I/O 8 39 IO I/O Bus I/O 2
3   n.c. 38   n.c.
4   n.c. 37 I Flag A
5   n.c. 36   n.c.
6   n.c. 35 I Strobe
7   n.c. 34 I S-Times D
8 V VDD (0 V) 33 I S-Times C
9 V VGG (-7 V) 32 I S-Times B
10 I Clock In 1 31 I S-Times A
11 I Clock In 2 30 I Condition Flag
12 V VSS (+10 V) 29   n.c.
13 O ROM Instruction B0 28 I P Register
14 O ROM Instruction B1 27 I Condition Flag B
15 O ROM Instruction B2 26 I Condition Flag A
16 O ROM Instruction B3 25 O ROM Instruction B12
17 O ROM Instruction B4 24 O ROM Instruction B11
18 O ROM Instruction B5 23 O ROM Instruction B10
19 O ROM Instruction B6 22 O ROM Instruction B9
20 O ROM Instruction B7 21 O ROM Instruction B8

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If you have additions to the above datasheet please email:

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