HP 3000 III Series Manual page 62

Sys tern/CPU Overv iew
2-35.
BIT TEST. The bit test instructions are also in subop-
code group 1 and use bits 5 through 9 to encode the specific in-
struction. Bits 10 through 15 specify a bit position in the TOS
word for testing. If the index bit (bit 4) is 1, the contents of
the X Register is added to the specified bit position.
2-36. MOVE. The move instructions use 12 of the codes specified
by the sub-opcode
group 2 code 0000. Sub-opcode group 2
is de-
fined by 0010 in the first four bits. Bits 8 through 10 encode
the specific move instruction. Bit 11 is used by some instruc-
tions to specify whether the source of the moved data is PB-rela-
tive (bit 11
=
0) or DB-relative (bi t 11
=
1). In some cases,
bit 11 is also used as an additional code bit for specifying the
instruction. Bits 12 and 13 are not used. Bits 14 and 15 are
used to specify an S-decrement value to delete, if desired, the
move parameters from the TOS.
2-37. SPECIAL. The special instructions use four mini-cpcodes.
The m ini-opcode group is also specified by the sub-opcode group 2
code 0000.
Bits
8 through 11 plus bit 15
encode the specific
special instruction. Bits 12 through 14 are not used.
2-38. IMMEDIATE. The immediate instructions use codes in both
sUb-op code
gr oup 2 (coded 0010)
and s ub- opcode
group 3
(coded
0011). Bits 4 through 7 encode the specific immediate instruc-
tion.
Bits 8 through 15 are used for the immediate operand.
2-39. FIELD. The field deposit and extract instructions are
specified by two of the sub-opcode group 2 codes. Bits 4 through
7 encode the specific field instruction. Bits 8 through
15 are
divided into a J-field and a K-field. The J-field specifies the
starting bit number and the K-field specifies the number of bits.
2-40. REGISTER CONTROL. The tegister control
bits 9 through 15 to name a register. Bits 4
the specific register control instruction.
instructions use
through 7 encode
2-41.
PROGRAM CONTROL. The program control instructions use four
of the sub-opcode group 3 codes. Sub-opcode group 3 is specified
by 0011 in the first four bits. Bits 4 through 7 encode the spe-
cific program control instruction. The N-field (bits 8 through
15) is used for either a PL-displacement (PCAL and SCAL) or to
specify a number of parameters to be deleted on return from a
procedure or subroutine (EXIT or SXIT).
2-42. I/O AND INTERRUPT. The I/O and interrupt instructions use
11 of the special
opcodes (bi ts 8 through
11)"
defined by the
subopcode group 3 code 0000. The K-field (bits 12 through 15) is
used by some of the instructions for an S-displacement to locate
a device number given in the stack.
2-43. LOOP CONTROL. The loop control instructions are defined by
a special coding of bits 4, 5, and 6 for memory opcode 05 (which
is otherwise defined as the STOR instruction). Bits 8 through 15
give a P-relative displacement for a branch address and bit 7
2-30