IA2910A
Data Sheet
Microprogram Controller
August 19, 2008
Instruction Set Description
I(3:0)
Mnemonic
Name
Reg/cntr Fail
Fail
Stack
Pass
Y
Pass
Stack
Reg/cntr
Enable
contents
Y
0
1
2
3
4
JZ
CJS
JMAP
CJP
PUSH
Jump Zero
Cond JSB PL
Jump Map
Cond Jump PL
Push/cond LD
cntr
X
X
X
X
X
0
PC
D
PC
PC
CLEAR
HOLD
HOLD
HOLD
PUSH
0
D
D
D
CLEAR
PUSH
HOLD
HOLD
PUSH
HOLD
HOLD
HOLD
HOLD
NOTE 1
PL
PL
MAP
PL
PL
PC
5
6
7
8
9
JSRP
CJV
Cond JSB
R/PL
Cond Jump
Vector
Cond Jump
R/PL
Repeat Loop,
Cntr .NE. 0
Repeat PL, cntr .NE. 0
.NE. 0
Cond RTN
Cond Jump PL
& POP
X
X
X
R
PUSH
D
D
D
PUSH
HOLD
HOLD
HOLD
PL
PC
R
HOLD
HOLD
HOLD
HOLD
VECT
PL
JRP
RFCT
RPCT
.NE. 0
= 0
F
PC
D
PC
PC
PC
HOLD
POP
HOLD
HOLD
HOLD
HOLD
F
HOLD
POP
HOLD
HOLD
POP
DEC
HOLD
DEC
HOLD
HOLD
HOLD
PL
PL
PL
PL
PL
PL
PC
D
PC
F
= 0
X
X
10
11
CRTN
CJPP
D
POP
12
LDCT
LD Cntr &
Continue
X
PC
HOLD
PC
HOLD
LOAD
PL
13
14
15
LOOP
CONT
TWB
Test End Loop
Continue
Three-Way
Branch
X
X
.NE. 0
= 0
F
PC
F
HOLD
HOLD
HOLD
POP
PC
PC
PC
PC
POP
HOLD
POP
HOLD
HOLD
DEC
PL
PL
PL
PL
D
POP
HOLD
NOTE 1: If CCENn is LOW and CCn is HIGH, HOLD; ELSE LOAD.
X = Don’t Care
.NE. = Not equal
Table 2
Instruction Set
The IA2910A provides sixteen instructions which select the address of the next microinstruction to
be executed. Four of the instructions are unconditional – their effect depends only on the
instruction. Ten of the instructions have an effect which is partially controlled by an external, data-
dependent condition. Three of the instructions have an effect which is partially controlled by the
contents of the internal register/counter. The instruction set is shown in Table 2. Examples of the
Instruction Execution are illustrated in Figure 2. In this discussion it is assumed that CIN is tied
HIGH.
In the ten conditional instructions, the result of the data-dependent test is applied to CCn. If the
CCn input is LOW, the test is considered to have been passed, and the action specified in the name
occurs; otherwise, the test has failed and an alternate (often simply the execution of the next
sequential microinstruction) occurs. Testing of CCn may be disabled for a specific microinstruction
by setting CCENn HIGH, which unconditionally forces the action specified in the name; that is, it
forces a pass. Other ways of using CCENn include (1) tying it HIGH, which is useful if no
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