2 0000 - Relative Jump
| (require ledum/bb68/op-0000-ctrl-jump) | package: ledum-bb68 |
private opcode
c = bb68-ccc
z : (integer-in -256 255)
c : (integer-in 0 7)
mask: f000 |
value: 0000 |
Performs a relative jump with a fixed delta of -256..+255 words.
According to the condition ”c”, the jump can be unconditional (c == 100) or depend on an ALU flag Z (c == 001), C (c == 010), S (c == 011), or its inverse (NZ: c == 101, NC: c == 110, NS: c == 111).
(The c == 000 condition would mean a jump that is never taken,
and is used as a predefined empty operation; the macroinstruction NOP
translates to this.)
A predefined empty operation that does not affect the CPU state
but consumes appropriate CPU cycles.
Internally, this is a macro that translates to JRE with zero delta and condition c == 000,
which is equivalent to two zero bytes in the machine code.
RETE – return from exception – restore flags, clear lower half of %emcf, jump to %erets:%eretp
stop execution and wait for an interrupt