Sinclair Scientific - TMC0805 Emulator

Current Address

000

Flags	A	9	8	7	6	5	4	3	2	1	0
A	○	○	○	○	○	○	○	○	○	○	○
B	○	○	○	○	○	○	○	○	○	○	○

Register	Mantissa									Exponent
A	0	0	0	0	0	0	0	0	0	0	0
B	0	0	0	0	0	0	0	0	0	0	0
C	0	0	0	0	0	0	0	0	0	0	0

Sinclair Scientific	1 rad	57•2958°
	ln 10	2•30259
	e	2•71828
	π	3•14159

▲	C

7	8	9	log

4	5	6	antilog tan

1	2	3	arctan sin

▼	0	E	arcsin cos

			arccos

What is this?

This is an emulation of the Sinclair Scientific, introduced in 1974 as the cheapest scientific calculator of the time, with poor accuracy. Built with a TMC0805, one of Texas Instrument's first "calculators on a chip".

I extracted the ROM directly off of a die of the chip. You can read more about that here.

Programmable Logic Array (PLA)

Texas Instruments was unique for including multple PLAs into their chip. This was like microcode added in addition to the ROM.

This emulator reads the PLA too. Here is the ALU PLA, which sets which opcode does which math operation:

Opcode	>>	<<	−	Hex	C	A	B	K	A=	C=	B=	A⇄B	Wait	Result
00						✓	✓		✓					A = A + B
01						✓		✓	✓					A = A + K
02						✓		✓		✓				C = A + K
03					✓		✓				✓			B = C + B
04							✓			✓				C = B
05					✓			✓	✓					A = C + K
06					✓			✓			✓			B = C + K
07			✓			✓	✓		✓					A = A - B
08			✓			✓	✓			✓				C = A - B
09			✓			✓		✓	✓					A = A - K
10			✓		✓		✓			✓				C = C - B
11			✓		✓			✓		✓				C = C - K
12			✓			✓	✓							A - B
13			✓			✓		✓						A - K
14			✓		✓		✓							C - B
15			✓		✓			✓						C - K
16								✓	✓					A = K
17								✓			✓			B = K
18								✓		✓				C = K
19												✓		A⇄B
20		✓				✓			✓					A = A << 4
21		✓					✓				✓			B = B << 4
22		✓			✓					✓				C = C << 4
23	✓					✓			✓					A = A >> 4
24	✓						✓				✓			B = B >> 4
25	✓				✓					✓				C = C >> 4
26						✓		✓	✓				✓	Wait A = A + K
27			✓		✓		✓		✓					A = C - B
28			✓		✓			✓			✓			B = C - K
29					✓			✓		✓				C = C + K
30						✓	✓			✓				C = A + B
31					✓		✓			✓				C = C + B
Opcode	>>	<<	−	Hex	C	A	B	K	A=	C=	B=	A⇄B	Wait	Result

When the result isn't being saved anywhere, then only the carry/borrow flag is set.

Source code

Acknowledgments / Resources

This emulation would be lacking without the resources below: