/* not -2047 or 2047), so 'b' needs to be adjusted to the expected 12-bit DQ value. Bear in mind that */
	/* bits 0 to 3 in 'dq' need to be zero, otherwise this will generate an illegal instruction. */
	/* If in doubt how this instruction form is encoded, refer to ISA 3.0b, pages 492 and 507. */
	dq := b >> 4
	return op | (xt&31)<<21 | (a&31)<<16 | (dq&4095)<<4 | (xt&32)>>2
}

/* Z23-form, 3-register operands + CY field */