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Operation Theorem
•
37
Control Byte
Before loading or reading any of these individual counters, the control
byte (BASE+3) must be loaded first. The format of the control byte is :
B
i
t
7
6
5
0
S
C
1
S
C
0
R
L
1
B
C
D
• SC1 & SC0 - Select Counter (Bit7 & Bit 6)
S
C
1
S
C
0
COUNTER
0
0
Select Counter 0
0
1
Select Counter 1
1
0
Select Counter 2
1
1
ILLEGAL
• RL1 & RL0 - Select Read/Load operation (Bit 5 & Bit 4)
R
L
1
R
L
0
OPERATION
0
0
COUNTER LATCH FOR STABLE READ
0
1
READ/LOAD LSB ONLY
1
0
READ/LOAD MSB ONLY
1
1
READ/LOAD LSB FIRST, THEN MSB
• M2, M1 & M0 - Select Operating Mode (Bit 3, Bit 2, & Bit 1)
M2 M1 M0 MODE
0 0 0 0
0 0 1 1
x 1 0 2
x 1 1 3
1 0 0 4
1 0 1 5