Editing general instrument/sba/isa

{{gi title|SBA ISA}}
{{isa box
| name           = SBA
| developer      = General Instrument
| implementation = SBA
| dev model      = proprietary
| design         = 
| data size      = 1 bit
| inst size      = 8 bit
| inst count     = 24
| introduction   = 1977
| version        = 1
| format         = stack
| endianness     = bi-endian
| registers      = 0
}}
The '''SBA ISA''' was an [[instruction set architecture]] used in the [[General Instrument]]'s {{gi|SBA}} family of {{arch|1}} [[microcontrollers]].

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

* With immediate: The 5 [[MSB]]s are reserved for the address, but only up to the 30th address. The opcode is stored in the 3 LSBs.
: <span style="border: 1px solid black; padding: 3px;">{{bin|00000}}-{{bin|11101}}</span><span style="border: 1px solid black;  padding: 3px;">{{bin|000}}-{{bin|111}}</span>
* Without immediate: Addresses 30 and 31 are reserved for extended instructions of 8 bits.
: <span style="border: 1px solid black; padding: 3px;">{{bin|11110000}}-{{bin|11111111}}</span>

This scheme allows for 30 addresses and 24 instructions (8 operating on [[immediate value]]s and 16 without immediates).

== Listing ==
{{isa
| title    = SBA ISA
| Opcode
| Action
| listing  =
{{inst|mn=ANDIN   |op={{bin|AAAAA000}} |act={{l|and|In[AAAAA]|Stack[Top]}}}}
{{inst|mn=NANDIN  |op={{bin|AAAAA001}} |act={{l|and|{{l|onot|In[AAAAA]}}|Stack[Top]}}}}
{{inst|mn=ANDSS   |op={{bin|AAAAA010}} |act={{l|and|Store[AAAAA]|Stack[Top]}}}}
{{inst|mn=NANDSS  |op={{bin|AAAAA011}} |act={{l|and|{{l|onot|Store[AAAAA]}}|Stack[Top]}}}}
{{inst|mn=ASP1    |op={{bin|AAAAA100}} |act={{l|and|Store[AAAAA]|Stack[Top]}} ; PUSH(1)}}
{{inst|mn=NASP1   |op={{bin|AAAAA101}} |act={{l|and|{{l|onot|Store[AAAAA]}}|Stack[Top]}} ; PUSH(1)}}
{{inst|mn=STORE   |op={{bin|AAAAA110}} |act=Store[AAAAA] = Stack[Top] ; Stack[Top] = 1}}
{{inst|mn=OUTPUT  |op={{bin|AAAAA111}} |act=Out[AAAAA] = Stack[Top] ; Stack[Top] = 1}}
{{inst|mn=RESTART |op={{bin|11110000}} |act=restarts evaluation of program}}
{{inst|mn=INVERT  |op={{bin|11110001}} |act=Stack[Top] = {{l|onot|Stack[Top]}}}}
{{inst|mn=PAGE    |op={{bin|11110010}} |act=Change page}}
{{inst|mn=HOME    |op={{bin|11110011}} |act=Back to home page}}
{{inst|mn=PUSH0   |op={{bin|11110100}} |act=PUSH(0)}}
{{inst|mn=PUSH1   |op={{bin|11110101}} |act=PUSH(1)}}
{{inst|mn=PUSHC   |op={{bin|11110110}} |act=PUSH(Stack[Top])}}
{{inst|mn=POP     |op={{bin|11110111}} |act=POP()}}
{{inst|mn=AND     |op={{bin|11111000}} |act=Stack[Top] = {{l|and|Stack[Top]|Stack[Top-1]}}}}
{{inst|mn=OR      |op={{bin|11111001}} |act=Stack[Top] = {{l|or|Stack[Top]|Stack[Top-1]}}}}
{{inst|mn=EXOR    |op={{bin|11111010}} |act=Stack[Top] = {{l|xor|Stack[Top]|Stack[Top-1]}}}}
{{inst|mn=COMP    |op={{bin|11111011}} |act=}}
{{inst|mn=PAND    |op={{bin|11111100}} |act={{l|and|PUSH(Stack[Top]|Stack[Top-1])}} ; Stack[Top] = 1}}
{{inst|mn=POR     |op={{bin|11111101}} |act={{l|or|PUSH(Stack[Top]|Stack[Top-1])}} ; Stack[Top] = 1}}
{{inst|mn=PEXOR   |op={{bin|11111110}} |act={{l|xor|PUSH(Stack[Top]|Stack[Top-1])}} ; Stack[Top] = 1}}
{{inst|mn=PCOMP   |op={{bin|11111111}} |act=}}
}}

== See also ==
* {{arch|1}}
* {{gi|SBA}}
designer	General Instrument +
first launched	1977 +
full page name	general instrument/sba/isa +
implementation	SBA +
instance of	instruction set architecture +
instruction count	24 +
instruction word size	8 bit (1 octets) +
name	SBA +
word size	1 bit (0.125 octets, 0.25 nibbles) +