Jameco Electronics Rabbit 3000 - Manual (Page 302)

User’s Manual 293
B.1.9 New Opcodes
Eight new opcodes were added to the Rabbit 3000A. UMA and UMS allow multiply-and-
add and multiply-and-subtract operations on large integers, and were added to speed up
common cryptographic math used in public-key calculations. The remaining six expand
the block copy operations available, especially to and from I/O addresses (internal and
external). These opcodes are listed in Table B-18.
B.1.9.1 New UMA/UMS Opcodes
The new UMA and UMS opcodes perform the following operation:
{CY:DE':(HL)} = (IX) ± [(IY) * DE + DE' + CY];
where HL, IX, and IY increment after each byte, repeated BC times. This fundamental
operation allows the addition or subtraction of two arbitrarily-long unsigned integers after
one is scaled by a single-byte value. This operation is common in many cryptographic
operations.
Table B-18. New Rabbit 3000 Opcodes
Instruction Bytes Clks A I S Z V C Operation
UMA 2 8+8i - - - - *
{CY:DE':(HL) = (IX) + [(IY) * DE + DE' + CY];
BC = BC-1; IX = IX+1; IY = IY+1; HL = HL+1;
repeat while BC !=0
UMS 2 8+8i - - - - *
{CY:DE:(HL) = (IX) - [(IY) * DE + DE' + CY];
BC = BC-1; IX = IX+1; IY = IY+1; HL = HL+1;
repeat while BC !=0
LDDSR 2 6+7i d - - * -
(DE) = (HL); BC = BC - 1; HL = HL - 1;
repeat while BC != 0
LDISR 2 6+7i d - - * -
(DE) = (HL); BC = BC - 1; HL = HL + 1;
repeat while BC != 0
LSDR 2 6+7i s - - * -
(DE) = (HL); BC = BC - 1; DE = DE - 1;
HL = HL - 1; repeat while BC != 0
LSIR 2 6+7i s - - * -
(DE) = (HL); BC = BC - 1; DE = DE + 1;
HL = HL + 1; repeat while BC != 0
LSDDR 2 6+7i s - - * -
(DE) = (HL); BC = BC - 1; DE = DE - 1;
repeat while BC != 0
LSIDR 2 6+7i s - - * -
(DE) = (HL); BC = BC - 1; DE = DE + 1;
repeat while BC != 0