CDP1855 Просмотр технического описания (PDF) - Intersil
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CDP1855 Datasheet PDF : 15 Pages
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BUS 7
BUS 6
BUS 5
CDP1855, CDP1855C
CONTROL REGISTER BIT ASSIGNMENT TABLE
BUS 4
BUS 3
BUS 2
BUS 1
BUS 0
REGISTER
RESET
B2 = 1, RESET Z REGISTER
B3 = 1, RESET Y REGISTER
B5
B4
NO. OF MDU’s
1
1
One MDU
1
0
Two MDU’s
0
1
Three MDU’s
0
0
Four MDU’s
B6 = 1, RESET SEQUENCE COUNTER
B7 = 1, SELECT SHIFT RATE OPTIONS:
B7 = 0, SHIFT = CLOCK FREQUENCY RATE
B1
B0
0
0
0
1
1
0
1
1
NO. OF MDU’s
1
2
3
4
OPERATION SELECT
No Operation
Multiply
Divide
Illegal State
SHIFT RATE
Clock ÷ 2
Clock ÷ 4
Clock ÷ 8
Clock ÷ 8
STATUS REGISTER
STATUS BYTE
BIT
7
6
5
4
3
2
OUTPUT
0
0
0
0
0
0
NOTES:
1. O.F. = 1 if overflow (only valid after a divide has been done)
2. Bits 1 - 7 are read as 0 always.
1
0
0
O.F.
DELAY NEEDED WITH AND WITHOUT PRESCALER
8N + 1 Shifts/Operation at 1 Clock Cycle/Shift
N = Number of MDU’s, S = Shift Rate
WITHOUT PRESCALER
WITH PRESCALER
NO. OF MDU’s
SHIFTS = 8N +1
NEEDED
(NOTE 1)
MACHINE CYCLES
NEEDED
SHIFTS = S (8N +1)
NEEDED
(NOTE 1)
MACHINE CYCLES
NEEDED
1
9
2 (1 NOP)
18
3 (1 NOP)
2
17
2 (1 NOP)
68
9 (3 NOPs)
3
25
3 (1 NOP)
200
25 (9 NOPs)
4
33
4 (2 NOPs)
264
33 (11 NOPs)
NOTE:
1. NOP instruction is shown for machine cycles needed (3/NOP). Other instructions may be used.
SHIFT RATE
2
4
8
8
4-53
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