GIM SBA
Developer	General Instrument
Manufacturer	General Instrument
Type	microcontrollers
Production	November, 1977
Architecture	1-bit
Word size	1-bit "-bit" is not declared as a valid unit of measurement for this property.
Technology	nMOS
Clock	10 kHz-800 kHz
Package	DIP40

The GI SBA (Sequential Boolean Analyzer) was a family of 1-bit microcontrollers developed by General Instrument's Microelectronics division. These microcontrollers served as cheap programmable logic controllers, replacing old relay system.

Members

Part	RAM	ROM	I/O Ports	Notes
SBA	120x1 bits	1024x8 bits	31
SBA-1	120x1 bits		31	external storage
SBA-2	120x1 bits	2048x8 bits	31	?ever released?

Architecture

The SBA family had 8-bit instructions of two types: with immediate and without immediate value.

• With immediate: The 5 MSBs are reserved for the address, but only up to the 30th address. The opcode is stored in the 3 LSBs.

00000₂-11101₂000₂-111₂

• Without immediate: Addresses 30 and 31 are reserved for extended instructions of 8 bits.

11110000₂-11111111₂

This scheme allows for 30 addresses and 24 instructions (8 operating on immediate values and 16 without immediates).

Stack

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Instruction Set

SBA ISA
Mnemonic
ANDIN	AAAAA0002	In[AAAAA] · Stack[Top]
NANDIN	AAAAA0012	In[AAAAA] · Stack[Top]
ANDSS	AAAAA0102	Store[AAAAA] · Stack[Top]
NANDSS	AAAAA0112	Store[AAAAA] · Stack[Top]
ASP1	AAAAA1002	Store[AAAAA] · Stack[Top] ; PUSH(1)
NASP1	AAAAA1012	Store[AAAAA] · Stack[Top] ; PUSH(1)
STORE	AAAAA1102	Store[AAAAA] = Stack[Top] ; Stack[Top] = 1
OUTPUT	AAAAA1112	Out[AAAAA] = Stack[Top] ; Stack[Top] = 1
RESTART	111100002	restarts evaluation of program
INVERT	111100012	Stack[Top] = Stack[Top]
PAGE	111100102	Change page
HOME	111100112	Back to home page
PUSH0	111101002	PUSH(0)
PUSH1	111101012	PUSH(1)
PUSHC	111101102	PUSH(Stack[Top])
POP	111101112	POP()
AND	111110002	Stack[Top] = Stack[Top] · Stack[Top-1]
OR	111110012	Stack[Top] = Stack[Top] + Stack[Top-1]
EXOR	111110102	Stack[Top] = Stack[Top] ⊕ Stack[Top-1]
COMP	111110112
PAND	111111002	PUSH(Stack[Top] · Stack[Top-1]) ; Stack[Top] = 1
POR	111111012	PUSH(Stack[Top] + Stack[Top-1]) ; Stack[Top] = 1
PEXOR	111111102	PUSH(Stack[Top] ⊕ Stack[Top-1]) ; Stack[Top] = 1
PCOMP	111111112

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