def doDEIMByte(byte):
global DPC, DX, DY, DRSindex
if byte & 0x80: # increment?
prevDX = DX
prevDY = DY
if byte & 0x20:
DX -= (byte & 0x18) >> 3
else:
DX += (byte & 0x18) >> 3
if byte & 0x04:
DY -= (byte & 0x03)
else:
DY += (byte & 0x03)
# if byte & 0x40:
# display.draw(0, prevDX, prevDY, DX, DY)
else: # micro instructions
if byte & 0x40:
mode = MODE_NORMAL
if byte & 0x20: # DRJM
if DRSindex <= 0:
Trace.comment('\nDRS stack underflow at display address %6.6o'
% (DPC - 1))
illegal()
DRSindex -= 1
DPC = DRS[DRSindex]
if byte & 0x10:
DX += 0x08
if byte & 0x08:
DX &= 0xfff8
if byte & 0x02:
DY += 0x10
if byte & 0x01:
DY &= 0xfff0
def illegal(instruction=None):
if instruction:
Trace.comment('Illegal display instruction (%6.6o) at address %6.6o'
% (instruction, (DPC - 1)))
else:
Trace.comment('Illegal display instruction at address %6.6o'
% (DPC - 1))
sys.exit(0)
def i_DRJM():
global DPC, DRSindex
if DRSindex <= 0:
Trace.comment('DRS stack underflow at display address %6.6o'
% (DPC - 1))
illegal()
DRSindex -= 1
DPC = DRS[DRSindex]
Trace.dtrace('DRJM')
def i_DJMS(address):
global DPC, DRSindex, DIB
if DRSindex >= 8:
Trace.comment('DRS stack overflow at display address %6.6o'
% (DPC - 1))
illegal()
DRS[DRSindex] = DPC
DRSindex += 1
DPC = MASK_MEM(address + (DIB << 12))
Trace.dtrace('DJMS', address)
return 1
