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Tandy PC-6

OverviewAssembler
There are no pictures available for this page. Maybe later?

I was browsing the manual when I found a rather intriguing chapter...

Chapter 8: assembler and Simulator Functions...

This thing allows programming in Assembly, but not it's own assembly, but on a theoretical computer.

Warning: The rest of this page will assume that you have a working knowledge of Binary, HEX and preferably also Assembler...


There is something strange in the manual, namely that they number the Most Significant Bit as 0 and the Least Significant Bit as 15. this is contrary to EVERY other manual that I have...

The PC-6 emulates a 16bit computer with a memory of 2048Words.(0 - 2047) This memory is split into 8 256word pieces called Blocks.(Numbered 0 - 7)

The Processor have these registers:
SC (Sequence Counter)
IR (Instruction register)
BR (Base Register)
OR (Operand register)
GR0 (General Register 0)
GR1 (General Register 1)
GR2 (General Register 2)
GR3 (General Register 3)
CC (Condition Code, 1bit)
Now for the explanation:

Every instruction is 16-bit in length and have this format:
(Real processors usually don't have such neat layout)
15141312111098 76543210
OPGRXRAD
The OP(operand) field contains the actual instruction. Here's the short list:
BinaryHexInstructionMnemonics
00000Halt and JumpHJ
00011Jump if GR is not ZeroJNZ
00102Jump on conditionJC
00113Jump to subroutineJSR
01004ShiftSFT
01015ReadREAD
01106WriteWRITE
10008Load Address ImmediateLAI
1010AAddADD
1011BSubtractSUB
1100CLoadLD
1101DStoreST
1110EAndAND
1111FExclusive orEOR
The GR field specifies the General register that will be the object of the instruction. However, the contents of the GR field will be disregarded in the case of "Halt and Jump" instruction and a decision condition for jumping will be meant in the case of a "jump on condition" instruction.


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