micro step of R1 chip  10 June 99

Each line is one time step.

Notation 
// comment line
name :    macro name
*name     macro expansion (substitute with macro body)
destination = source    single transfer of data between two registers
e1 ; e2   event 1 is concurrent with event 2
M[ads]    memory at address specified by register ads

Registers :  mar, mdr, ir, ip, sp, fp, x, y, z 
mar	memory address register
mdr	memory data register
ir	instruction register
ip	instruction pointer (program counter)
sp	stack pointer
fp	frame pointer
x,y,z	alu registers

ALU : alu( function )

Begin the micro steps

main :
while ( 1 ) {
  *ifetch
  ir = mdr 
  switch( ir ) {
  0 : *lit
  1 : *lval
  . . .
  }
}

ifetch : 
mar = ip
mdr = M[mar] ; ip++

push :
sp++
mar = sp
M[mar] = mdr

pushx :
mdr = x
*push

pushz :
mdr = z
*push

pop :
mar = sp
mdr = M[mar] ; sp--

popx :
*pop
x = mdr

popy :
*pop
y = mdr

lit :
*ifetch   // fetch arg
*push

lval :
*ifetch   // fetch arg
x = fp
y = mdr
z = alu(+)
*pushz

lvalg :  // same as *lit

rval :
*ifetch
x = fp
y = mdr
z = alu(+)
mar = z
mdr = M[mar]
*push

rvalg :
*ifetch  
mar = mdr
mdr = M[mar]
*push

fetch :  (ads -- val)
mar = sp
mdr = M[mar] ; sp--
mar = mdr
*push

set : (ads,val - - )
*popx
*popy
mar = x
mdr = y
M[mar] = mdr

index :  // is same as *add

jmp :
*ifetch
ip = mdr

jz :
*ifetch
if cond then ip = mdr

call : ( - - retads)
mdr = ip
*push

// ---------- stack frame----
hi ads
sp ->   top of stack
        stack area
        sp'
        ip'
fp ->   fp'
        local var
// --------------------------------

func : 
x = sp
mdr = fp
*push     // push fp
fp = sp
mdr = ip
*push     //  push ip
*pushx    // push sp
sp++

ret0 : 
sp = fp
mar = fp ; sp++
mdr = M[mar]
fp = mdr   // pop fp'
mar = sp
mdr = M[mar] ; sp++
ip = mdr   // pop ip'
mar = sp
mdr = M[mar]
sp = mdr  // pop sp'

ret1 :
*popx
*ret0
*pushx

add :
*popx
*popy
z = alu(+)
*pushz

Other instructions not yet implemented :

sub, mul, div, minus, not, and, or, 
lt, le, eq, ne, ge, gt
in, out