[SOLVED] CS assembly All registers and memory locations are 32 bits, the concept of byte does not apply except in the few special string-processing instructions. When characters are stored to make a string, they are packed four per memory location, with the first character of the string being in the least-significant 8 bits.

All registers and memory locations are 32 bits, the concept of byte does not apply except in the few special string-processing instructions. When characters are stored to make a string, they are packed four per memory location, with the first character of the string being in the least-significant 8 bits.
Negative numbers are represented in the twos complement format.
Floating point numbers are stored in the intel 32-bit floating format, whatever that is.
Bits are numbered from 0, the least significant, to 31 the most significant. In numeric representations, bit 31 is the sign bit.
There are 16 regular registers, numbered from 0 to 15.
R0 is a scratch register, with slightly limited functionality
R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12 are general purpose registers SP, the stack pointer, is encoded as register 13
FP, the frame pointer, is encoded as register 14
PC, the program counter, is encoded as register 15
The instruction format
I is the Indirect bit. Twos complement, range -32768 to +32767
If bits 16-19 are all zero, i.e. Index Register indicates R0, then no index register is used when the instruction executes. Thus it is not possible to use R0 as an index register.
In the description of an instruction, the term reg refers to the register indicated by bits 20 to 23 (main register), and operand refers to the combination of indirect bit, index register, and numeric operand as illustrated on the next two pages.
If the term value appears in the description, it refers to the value of the operand, which is calculated as follows:
part1 = numeric operand; part2 = 0;
if (index register 0)
part2 = contents of indicated index register total = part1 + part2;
if (indirect bit 0)
value = contents of memory location [total];
else
value = total;
If the sequence reg x appears, it means that the content of the main register is replaced by x.
If the sequence destination x appears, then the operand my consist of just an index register, in which case the content of the register is replaced by x, otherwise the indirect bit must be set, and the content of memory location [total] is replaced by x.
Operation
I
Main Register
Index Register
Numeric Operand
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

Assembly Examples:
RET
0100101 0 0000 0000 0000000000000000 4AOOOOOO
INC R6
0000100 0 0110 0000 0000000000000000 O86OOOOO
LOAD R2, 36
0000001 0 0010 0000 0000000000100100 O22OOO24
ADD R7, R3
0000110 0 0111 0011 0000000000000000 OC73OOOO
LOAD R7,R3+12
0000001 0 0111 0011 0000000000001100 O273OOOC
ADD R4, [R3]
0000110 1 0100 0011 0000000000000000 OD43OOOO
STORE R2, [1234]
0000011 1 0010 0000 0000010011010010 O72OO4D2
STORE R2, [R5 375]
0000011 1 0010 0101 1111111010001001 O725FE89
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
Operation Indirect bit Main register Index register Numeric
= 37 =0 =0 =0 =0
=4 =0 =6 =0 =0
=1 =0 =2 =0 =36
=6 =0 =7 =3 =0
=1 =0 =7 =3 =12
=6 =1 =4 =3 =0
=3 =1 =2 =0
= 1234
=3 =1 =2 =5
= -375

Execution Examples, starting from these values already in memory:
location
contents
27100 592
27101 759
27102 43
27103 27105
27104 2
27105 682
27106 11
27107 22
27108 33
LOADR2, 5
LOADR3, R2+4
LOADR4, 27102
LOADR5, [27100]
LOADR6, [R4]
ADD R6, R2
STORE R6, [27101]
INC R6
STORE R6, [R4 2]
LOADSP, 27108
PUSHR2
PUSH[R4]
POP R4
STORE R6, 27101
The value
The value
The value
The value
The value
The value
The content of memory location 27101 is changed from 759 to 48 The value stored in register 6 is now 49
stored in register 2 is now 5 stored in register 3 is now 9 stored in register 4 is now 27102 stored in register 5 is now 592 stored in register 6 is now 43 stored in register 6 is now 48
The content of memory location 27100 is changed from 592 to 49 The value stored in register 13 (stack pointer) is now 27108
The content of memory location 27107 is changed from 22 to 5 The value stored in register 13 (stack pointer) is now 27107
The content of memory location 27106 is changed from 11 to 43 The value stored in register 13 (stack pointer) is now 27106
The value stored in register 4 is now 43
The value stored in register 13 (stack pointer) is now 27107
Fails to execute, as the operand does not address memory.

opcode mnemonic
0 HALT
1 LOAD reg, operand
2 LOADH reg, operand
3 STORE reg, operand
action
the processor is halted, execution of instructions stops.
reg value
reg ( reg FFFF ) + ( value 16 )
the most significant 16 bits of the register are replaced
destination reg
destination value + 1
destination value 1
reg reg + value
reg reg value
reg reg value
reg reg value
reg reg modulo value
reg value reg
reg value reg
reg value modulo reg
reg reg value
reg reg value
reg reg value
reg ~ value
flagZ 1 if most sig. (value) bits of reg all 0, otherwise 0 reg reg value, zeros being inserted at the right
flagZ 1 if least sig. (value) bits of reg all 0, otherwise 0 reg reg value, zeros being inserted at the left
flagZ 1 if reg = value, otherwise 0 flagN 1 if reg < value, otherwise 0flagZ 1 if value = 0, otherwise 0 flagN 1 if value < 0, otherwise 0flagZ valueth bit of reg valueth bit of reg 1 valueth bit of reg 0 4 INC5 DEC6 ADD7 SUB8 MUL9 DIVoperandoperand reg, operand reg, operand reg, operand reg, operand reg, operand10 MOD11 RSUB reg, operand12 RDIV reg, operand13 RMOD reg, operand14 AND reg, operand15 OR reg, operand16 XOR reg, operand17 NOT reg, operand18 SHL reg, operand19 SHR reg, operand20 COMP reg, operand21 COMPZ operand22 TBIT reg, operand23 SBIT reg, operand24 CBIT reg, operand25 26 27 28 290 1 2 3 4 5 630 31 32 33 34JUMP operand JZER reg, operand JPOS reg, operand JNEG reg, operand JCONDJCOND EQL, operand JCOND NEQ, operand JCOND LSS, operand JCOND LEQ, operand JCOND GTR, operand JCOND GEQ, operand JCOND ERR, operandGETFL reg, operand SETFL reg, operand GETSR reg, operand SETSR reg, operand PUSH operandPC value if(reg=0)PCvalue if (reg0)PCvalue if(reg<0)PCvalueNote that no main register is used with the JCOND instruction. Instead, its 4 bits are used to encode one of the seven condition tests shown here.if(flagZ)PCvalueif (~flagZ ) PC value if(flagN)PCvalueif (flagZflagN) PCvalueif ( ~flagZ ~flagN ) PC value if(~flagN)PCvalue if(flagE)PCvaluereg flag[value]flag[value] regreg specialregister[value]specialregister[value] regSP SP1 memory[SP] valuedestination memory[SP] SP SP+1SP SP1 memory[SP] PC PC valuePC memory[SP] SP SP+1value is treated as a memory address. The regth 8-bit byte (character) starting from that address in memory is loaded into reg. i.e.,reg byte (reg modulo 4) of memory[value + reg4]value is treated as a memory address. The regth 8-bitbyte (character) starting from that address is replaced by the value of register 0 without modifying the other 24 bits of that word.byte (reg modulo 4) of memory[value + reg4] R0 Control peripheral activity: see separate documentation all flags reg3536 CALL37 RET 38 LDCH39 STCH40 PERIreg, operandreg, operand42FLAGSJ reg, operandPOP operand operand43 WAIT44 PAUSE45 BREAK46 IRETPC valueCPU idles until interruptedCPU idles for approximately 50mS, unless interrupted Enter CPU single-stepping modeall flags memory[SP+1] PC memory[SP+5]FP memory[SP+6]SP memory[SP+7]R12 memory[SP+8] R11 memory[SP+9] R10 memory[SP+10] R9 memory[SP+11] R8 memory[SP+12] R7 memory[SP+13] R6 memory[SP+14] R5 memory[SP+15] R4 memory[SP+16] R3 memory[SP+17] R2 memory[SP+18] R1 memory[SP+19] R0 memory[SP+20] SP SP+2147 SYSCALL reg, codememory[SP-1]memory[SP-2]memory[SP-3]memory[SP-4]memory[SP-5]memory[SP-6]memory[SP-7]memory[SP-8]memory[SP-9]memory[SP-10] R9memory[SP-11] R10memory[SP-12] R11memory[SP-13] R12memory[SP-14] SPmemory[SP-15] FPmemory[SP-16] PCmemory[SP-17] regmemory[SP-18] main register number memory[SP-19] codememory[SP-20] all flagsmemory[SP-21] 40SP SP21PC memory[specialregister[CGBR] + code] flagSys 1 R0 R1 R2 R3 R4 R5 R6 R7 R848 ATAS reg, operand49 PHLOAD reg, operand50 PHSTORE reg, operand51 VTRAN reg, operand52 MOVE reg, reg253 FADD reg, operand54 FSUB reg, operand55 FMUL reg, operand56 FDIV reg, operand57 FCOMP reg, operand58 FCOMPZ reg, operand59 FIX reg, operand60 FRND reg, operand61 FLOAT reg, operand62 FLOG reg, operand63 FEXP reg, operand64 FFO reg, operand65 FLZ reg, operand66 RAND regreg value ; destination 1performed indivisibly, ignoring interruptsreg physicalmemory[value] physicalmemory[value] regreg physical address for virtual address valuewhile R0 > 0 repeat
{ memory[reg2] memory[reg]
reg2 reg2 + 1 reg reg + 1 R0 R0 1 }
floating point: reg reg + value floating point: reg reg value floating point: reg reg value floating point: reg reg value
floating point:
flagZ 1 if reg = value, otherwise 0 flagN 1 if reg < value, otherwise 0floating point:flagZ 1 if reg = 0, otherwise 0 flagN 1 if reg < 0, otherwise 0reg (int)value, value interpreted as floating point reg (float)(closest int to value), both floating point reg (float)value, value interpreted as an integerfloating point:regnaturallog(reg), if value=0 reg log base value(reg), otherwisefloating point:regetopower(reg), if value=0 reg value to power(reg), otherwisereg number of bits to right of first 1 in value if value = 0: reg 1, flagZ 1, flagN 1reg number of bits to right of last 0 in value if value =1: reg 1, flagZ 1, flagN 1reg random positive number67 TRACE reg, operand68 TYPE operand69 INCH operand70 ANDN reg, operand71 ORN reg, operand72 NEG reg, operand73 FNEG reg, operand74 ROTL reg, operand75 ROTR reg, operand76 ASR reg, operand77 EXBR reg, operand78 EXBRV reg, operand79 DPBR reg, operand80 DPBRV reg, operand81 ADJS reg, operand82 UEXBR reg, operand83 UEXBRV reg, operand84 UCOMP reg, operand85 UMUL reg, operand86 UDIV reg, operand87 UMOD reg, operand88 CLRPP operand89 FILL reg, operanddisplay PC, reg, and value on consolesend single character value to controlling teletypedestination one character code from controlling keyboard or 1 if none availableregreg~valueregreg~valuereg valuereg value, value interpreted as floating pointreg is shifted value bits left, with the bits lost at the left being reinserted at the right.reg is shifted value bits right, with the bits lost at the right being reinserted at the left.flagZ 1 if least sig. (value) bits of reg all 0, otherwise 0 reg reg value, the sign bit being duplicated at the leftR0 bit range described by reg from value,with the most significant bit of the range giving the sign.R0 bit range described by reg of value,with the most significant bit of the range giving the sign.bit range described by reg from value R0. bit range described by reg of value R0.the bit range selector in reg is advanced by value positions, taking into account the range size and the requirement for ranges not to span two words. value may be negative.R0 bit range described by reg from value, unsigned. R0 bit range described by reg of value, unsigned.flagZ 1 if reg = value, otherwise 0flagN 1 if reg < value, otherwise 0, an unsigned comparisonreg reg value, unsignedreg reg value, unsignedreg reg modulo value, unsignedpage containing physical address value all set to zerowhile R0 > 0 repeat
{ memory[reg2] value

reg reg + 1 R0 R0 1 }