Talk:360 Assembly/Branch Instructions

In the Example of using a table of 2 byte offsets, there is this instruction.

ICM  R15,3,TABLE1(R15)   extract two byte offset into low order bits of R15

ICM is a RS type instruction of 4 bytes in length and is in the format OP R1,M3,D2(B2) The above attempted instruction is invalid and will result in an Assembler error.

I would suggest replacing the above invalid instruction with: LH   R15,TABLE1(R15)     GET 2 BYTE OFFSET
 * Done !

Note to whomever wrote the above note: ICM is a 370 instruction not supported by S/360.
 * -- Mike Housky, May 24, 2019, info+wikibooks at housky.net

Index register branch/no-branch description wrong
The BC instruction will branch when the index register is zero. In fact, nearly every BC instruction ever coded has a zero index register.

The only form of a BC instruction that will never branch is when the mask field is zero.

A zero index or base register field simply means that no register value is added to the effective address.
 * Mike Housky, May 24, 2019, info+wikibooks at housky.net

68.4.103.151 (discuss) 19:44, 24 May 2019 (UTC)