Texas Instruments TMC0580 DSCOM (Double Scanning and Read-Only Memory) Chip


With the introduction of the SR-51-II in 1976 the original 28-pin DIP (Dual Inline Package) encapsulation used for the TMC0501 Arithmetic Chip was changed to a 28-pin SDIP (Shrink Dual Inline Package) roughly the size of a standard 20-pin DIP encapsulation and the TMC0580 DSCOM (Double Scanning and Read-Only Memory) Chip more than doubled the capacity of the larger TMC0520/TMC0530 SCOM Chips from 1k*13 Bits to 2.5k*13 Bits in a 28-pin SDIP housing paving the way for the TI Programmable 59.

The TMC0580 DSCOM Chip integrates 2.5*13 Bits Instruction Memory with serial interface to the TMC0501E Enhanced Arithmetic Chip, 32 Constants mainly used for the calculation of transcendental functions with 16 digits, each accessible through a 4-bit bidirectional I/O bus and outputs for 16-digit display scanning. In addition to the 5 Registers of the TMC0501E Enhanced 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. The DSCOM Chip not only doubled the number of additional Registers but increased them from two to eight.

While the design of the TMC0580 DSCOM Chip would allow the use of multiple devices in one product, were most designs implemented with two TMC0580 and additional TMC0560 BROM Chips to increase program memory to the maximum addressable capacity of 8k*13 Bits. Only the SR-60A Prompting Desktop Calculator makes use of three DSCOM Chips..

Communication between the TMC0501E Enhanced Arithmetic Chip and the other family members of the TMC0500 Building Blocks for Scientific and Programmable Calculators is realized with multiple means:

IDLE, CLK 1 and CLK 2 Outputs are used to synchronize all peripherals connected to the TMC0501E Enhanced Arithmetic Chip with the 16 States of its Instruction Cycle
EXT Output indicates that the TMC0501E Enhanced Arithmetic Chip is addressing external memories/registers
IRG Input to receive the 13-bit Instruction Words from the ROM of the TMC0580
4-bit bidirectional I/O Bus I/O 8, I/O 4, I/O 2, and I/O 1 to communicate with registers

QUICK-LINK to TMS0500 Family.

Family Members and Applications

Type Calculators Function
TMC0582 TI-58, TI-59 DSCOM 1, with TMC0571
TMC0583 TI-58, TI-59 DSCOM 2, with TMC0571
TMC0584 SR-60A DSCOM 1
TMC0585 SR-60A DSCOM 2
TMC0586 SR-60A DSCOM 3
TMC0587 TI-5230 DSCOM 1, with TMC0572
TMC0588 TI-5230 DSCOM 2, with TMC0572
TMC0580/CD2400 TI-58C DSCOM 1, with TMC0573
TMC0580/CD2401 TI-58C DSCOM 2, with TMC0573


Revision Products First Prototypes Comments
TMC0581 SR-51-C (SR-51 II)   Initial design
TMC0581 Rev A SR-51-C (SR-51 II) May 1976 6 [:] 0 [=] [SUM] → {INV] [SUM]
TMC0581 Rev B SR-51-C (SR-51 II) August 1976  
TMC0582 SR-52 II (TI-59) December 1976 Initial design, DSCOM 1
TMC0582 Rev A
TMC0523 Rev A
SR-52 II (TI-59) January 1977 Card protecting, etc.
TMC0582 Rev B
TMC0523 Rev A
SR-52 II (TI-59) March 1977  
TMC0583 SR-52 II (TI-59) December 1976 Initial design, DSCOM 2
TMC0583 Rev A
TMC0523 Rev A
SR-52 II (TI-59) January 1977 Card protecting, etc.
TMC0583 Rev B
TMC0523 Rev A
SR-52 II (TI-59) March 1977  
TMC0584 SR-60A May 1977 Initial design, DSCOM 1
TMC0584 Rev A
TMC0523 Rev A
SR-60A July 1977 Card protecting, etc.
TMC0585 SR-60A May 1977 Initial design, DSCOM 2
TMC0586 SR-60A May 1977 Initial design, DSCOM 3

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 TMC0580 was manufactured in a 6 um metal gate PMOS process (metal width = 0.25 mil / 6.0 um, metal spacing = 0.30 mil / 8.0 um, diffusion width = 0.25 mil / 6.0 um, diffusion spacing = 0.30 mil / 8.0 um).
The die size of the TMC0580 is approximately 215 mils * 220 mils / 5.4 mm * 5.6 mm.


The TMC0580 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 Digit driver 15 28 O Digit driver 14
2 V Negative Voltage VGG 27 O Digit driver 13 (OVER)
3 V Negative Voltage VDD 26 O Digit driver 12 (M-MSD)
4 IO SCOM Interface D0 25 O Digit driver 11
5 IO SCOM Interface D1 24 O Digit driver 10
6 IO SCOM Interface D2 23 O Digit driver 9
7 IO SCOM Interface D3 22 O Digit driver 8
8 O Instruction words 21 O Digit driver 7
9 I Calculating status 20 O Digit driver 6
10 I External access 19 O Digit driver 5
11 I Clock Input 2 18 O Digit driver 4
12 I Clock Input 1 17 O Digit driver 3 (M-LSD)
13 V Common Voltage 16 O Digit driver 2 (E-MSD)
14 O Digit driver 0 15 O Digit driver 1 (E-LSD)

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,

Example for TI-58 and TI-59: 

D0 (?)    (?)        
D2    2nd INV lnx   CE  CLR
D3    LRN  x<>t  x2    √x  1/x
D4    SST  STO RCL    SUM  yX
D5    BST  EE  (    )  ÷
D6    GTO  7  8    9  ×
D7    SBR  4  5  TI58!  6  −
D8    RST  1  2    3  +
D9    R/S  0  .    +/−  =
D10          Card Sense    
D12  (?)   (?)         
D15  (?)    (?)        

Comments: The TI-58 is identified by a diode between D7 - KR, the TI-59 detects the Card Sense switch between D10 - KR. The (?) nodes are used to detect PRINT, PAPER ADVANCE and TRACE on the PC-100A.

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If you have additions to the above datasheet please email:

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