DATAMATH CALCULATOR MUSEUM
Texas Instruments announced on September 16, 1975 with the SR-52 their first Keystroke Programmable Handheld Calculator based on the TMC0500 Building Blocks for Scientific and Programmable Calculators introduced already in January 1974 with the SR-50 Slide Rule calculator. While the SR-50 used only the minimum configuration of this groundbreaking architecture 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 plus power supply and clock generation, went the SR-52 a step ahead and made full use of the TMC0500 Building Blocks. A closer look at the PCB (printed circuit board) of the SR-52 reveals a total of seven PMOS (P-channel Metaloxide Semiconductor) chips:
TMC0501: Arithmetic Chip Register Processor with five 16-digit Registers and segment decoder/driver
TMC0524: 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, two 16-digit Registers and 16-digit display scanning
TMC0562, TMC0563: Two TMC0560 Bare Read-Only Memory Chips 1,024*13 Bits Instruction Memory with serial interface to Arithmetic Chip, each for a combined 3,072*13 Bits Instruction Memory
TMC0595: Magnetic I/O Chip Four channel interface for magnetic card reader to save and load programs with up to 224 steps
TMC0599*2: Two Multi-Register Chips 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
Texas Instruments introduced together with the calculator a matching "Printer Cradle" PC-100 with an integrated alphanumerical printer capable to print up to 20 characters per line at a speed of three lines per second on a 2.5 inch wide thermal paper. The SR-52 calculator connects to the PC-100 printer cradle with a 12-pin connector accessible through its battery compartment and featuring all TMC0500 signals necessary to communicate to two additional PMOS chips hosted on the PC-100 PCB:
TMC0561, TMC0569: Two
TMC0560 Bare Read-Only Memory Chips 1,024*13
Bits Instruction Memory with serial interface to Arithmetic Chip for all commands responsible for printing and tracing
TMC0251: TMC0250 Printer/Display Chip Interface to Thermal Printer Mechanism
The SR-60 Prompting Desktop calculator introduced in 1976 took the architecture of the SR-52 even a step further and integrated an alphanumeric display and keyboard with even more Instruction and Data/program memory into a large but elegant housing.
The TMC0595 Magnetic I/O Chip provides the interface between the four-track magnetic card read/write mechanism and the TMC0501 Arithmetic Chip. Communication between the two chips is realized with multiple means:
IDLE, PHI 1 and PHI 2
Signals are used to synchronize all peripherals connected to the
TMC0501 Arithmetic Chip with the 16 States of its Instruction Cycle
EXT Output indicates that the TMC0501 Arithmetic Chip is addressing external memories/registers
IRG Input to receive the 13-bit Instruction Words from the Instruction Memory
The TMC0595 Magnetic I/O Chip also conditions the signals to and from the magnetic card read/write mechanism (e.g. motor, card sensor input, channel 1-4) to make them compatible with PMOS logic levels.
The card speed of the SR-52 is set at 3.8 IPS (inches per second), the calculator will function at a card speed of 3.3 IPS to 4.3 IPS. At any speed below 3.3 IPS, the magnetic head cant generate the required voltage to drive the TMC0595 Magnetic I/O Chip. At any speed above 4.3 IPS, the write length exceeds the usable length of the card.
In the TMC0595 Magnetic I/O Chip, to read and write properly, the reference voltage -VB (Pin 18) must be maintained within a tight tolerance:
TMC0595 Rev B: -VB = -5.1V ± 5%
TMC0595 Rev C: -VB = -3.3V ± 5%
TMC0595 Rev D: -VB = -VBAT
The TMC0595 Magnetic I/O Chip was replaced in 1977 with the TMC0594 Magnetic I/O Chip dropping the tight tolerances of the reference voltage -VB and using external preamplifiers for the track signals while reading magnetic cards.
QUICK-LINK to TMS0500 Family.
Reference Voltage -5.1 V
|TMC0595 Rev A||SR-52||Reference Voltage -5.1 V|
|TMC0595 Rev B||SR-52||March 1975||Reference Voltage -5.1 V|
|TMC0595 Rev C||SR-52, SR-60||April 1975||Reference Voltage -3.3 V|
|TMC0595 Rev D||SR-52A||July 1975||Reference Voltage -VBAT|
|TMC0595 Rev E||SR-52 II (TI-59)||October 1976||External Amplifier
Renamed to TMC0594
|PHI1, PHI2||225||230||kHz||Opposite phases|
The TMC0595 uses a standard 0.4 wide 22-pin DIP (Dual In-line Package with a 0.1 / 2.54 mm lead pitch).
|1||A||R/W Track 2||22||A||R/W Track 3|
|2||A||Capacitor Track 2||21||A||Capacitor Track 3|
|3||A||R/W Track 1||20||A||R/WTrack 4|
|4||A||Capacitor Track 1||19||A||Capacitor Track 4|
|5||V||Common Voltage||18||V||Reference Voltage|
|6||O||Instruction words||17||V||Common Voltage|
|7||I||Calculating status||16||I||External access|
|8||O||Keyboard emulation||15||I||Clock Input 2|
|9||O||Motor on/off||14||I||Clock Input 1|
|10||I||Card Sensing Input||13||V||Negative Voltage VDD|
|11||O||Lamp (not connected)||12||V||Negative Voltage VGG|
If you have additions to the above datasheet please email: email@example.com.
© Joerg Woerner, February 02, 2001. No reprints
without written permission.