MA2910
3
FAIL CCEN =
PASS CCEN =
I3 - I0
MNEMONIC
NAME
REGISTER LOW & CC =
HIGH & CC =
REGISTER/
ENABLE
/CONTROL HIGH
LOW
CONTROL
Y
STACK
Y
STACK
0
JZ
JUMP ZERO
X
0
CLEAR
O
CLEAR
HOLD
PL
1
CJS
COND JS P PL
X
PC
HOLD
D
PUSH
HOLD
PL
2
JMAP
JUMP MAP
X
D
HOLD
D
HOLD
HOLD
MAP
3
CJP
COND JUMP PL
X
PC
HOLD
D
HOLD
HOLD
PL
4
PUSH
PUSH/COND LD
X
PC
PUSH
PC
PUSH
Note 1
PL
CNTR
5
JSRP
COND JSB R/PL
X
R
PUSH
D
PUSH
HOLD
PL
VECTOR
6
CJV
COND JUMP
X
PC
HOLD
D
HOLD
HOLD
VECT
7
JRP
COND JUMP R/PL
X
R
HOLD
D
HOLD
HOLD
PL
8
RFCT
REPEAT LOOP
≠ 0
F
HOLD
F
HOLD
DEC
PL
CNTR
≠ 0
.
= 0
PC
POP
PC
POP
HOLD
PL
9
RPCT
REPEAT PL,
≠ 0
D
HOLD
D
HOLD
DEC
PL
CNTR
≠ 0
= 0
PC
HOLD
PC
HOLD
HOLD
PL
10
CRTN
COND RTN
X
PC
HOLD
F
POP
HOLD
PL
11
CJPP
COND JUMP PL
X
PC
HOLD
D
POP
HOLD
PL
& POP
12
LDCT
LD CNTR &
X
PC
HOLD
PC
HOLD
LOAD
PL
CONTINUE
13
LOOP
TEST END LOOP
X
F
HOLD
PC
POP
HOLD
PL
14
CONT
CONTINUE
X
PC
HOLD
PC
HOLD
HOLD
PL
15
TWB
THREE-WAY
≠ 0
F
HOLD
PC
POP
DEC
PL
BRANCH
= 0
D
PO P
PC
POP
HOLD
P L
Note 1: If CCEN = LOW & CC = HIGH, hold, else load.
FULL
(stack full)
The active low output FULL indicates that 9 items have
been loaded onto the stack .
PL
, MAP & VECT (pipeline, map and vector)
These active low outputs are set according to the
instruction being executed. At any time only one is active.
They may be used to select from one of three possible
external sources for microprogramme jumps, being used
directly as three-state enables for these sources.
Typically: PL enables the primary source of
microprogramme jumps, usually part of a pipeline register;
MAP
enables a PROM which maps an instruction to a
microcode starting location; VECT enables an optional third
source, after a vector from DMA or interrupt source.
Y (0 to 11) (Microcode address)
This is a 12 bit wide tristate output bus. It carries the
microcode address generated according to the instruction
read in from the I bus. OE can be used to put the bus in a high
impedance state. This allows another to take control of the
microcode address bus.
OE
(Output enable)
This active low input is used to enable the 12 lines of the Y
bus.
CP (Clock Pulse)
A LOW-to-HlGH transition on this input is used to trigger all
state changes within the device.
Figure 2: Table of Instructions
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