Maxim MAX12557 TV Converter Box User Manual


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MAX12557
Dual, 65Msps, 14-Bit, IF/Baseband ADC
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BINARY-TO-GRAY CODE CONVERSION
1) THE MOST SIGNIFICANT GRAY-CODE BIT IS THE SAME
AS THE MOST SIGNIFICANT BINARY BIT.
01 10 0100 1100 BINARY
GRAY CODE0
2) SUBSEQUENT GRAY-CODE BITS ARE FOUND ACCORDING
TO THE FOLLOWING EQUATION:
D13 D7 D3 D0
GRAY
X
= BINARY
X
+
BINARY
X + 1
BIT POSITION
0110 0100 1100 BINARY
GRAY CODE0
BIT POSITION
GRAY
12
= BINARY
12
BINARY
13
GRAY
12
= 1 0
GRAY
12
= 1
1
3) REPEAT STEP 2 UNTIL COMPLETE:
01 10 0100 1100 BINARY
GRAY CODE0
BIT POSITION
GRAY
11
= BINARY
11
BINARY
12
GRAY
11
= 1 1
GRAY
11
= 0
10
4) THE FINAL GRAY-CODE CONVERSION IS:
01 10 0100 1100 BINARY
GRAY CODE0
BIT POSITION
101 11 01 1010
GRAY-TO-BINARY CODE CONVERSION
1) THE MOST SIGNIFICANT BINARY BIT IS THE SAME AS THE
MOST SIGNIFICANT GRAY-CODE BIT.
2) SUBSEQUENT BINARY BITS ARE FOUND ACCORDING TO
THE FOLLOWING EQUATION:
BINARY
X
= BINARY
X+1
BIT POSITION
BINARY
12
= BINARY
13
GRAY
12
BINARY
12
= 0 1
BINARY
12
= 1
3) REPEAT STEP 2 UNTIL COMPLETE:
4) THE FINAL BINARY CONVERSION IS:
01 0 0 1110 1010
BINARY
GRAY CODE
BIT POSITION
0 BINARY
GRAY CODE01 0 0 11 01 1010
BINARY
11
= BINARY
12
GRAY
11
BINARY
11
= 1 0
BINARY
11
= 1
GRAY
X
0101 1110 1010
BINARY
GRAY CODE
0
BIT POSITION
1
01 0 11101010
BINARY
GRAY CODE
0
BIT POSITION
11
01 1 1 0100 1100
AB Y=AB
00
01
10
11
0
1
1
0
EXCLUSIVE OR TRUTH TABLE
WHERE IS THE EXCLUSIVE OR FUNCTION (SEE TRUTH
TABLE BELOW) AND X IS THE BIT POSITION:
+
WHERE IS THE EXCLUSIVE OR FUNCTION (SEE TRUTH
TABLE BELOW) AND X IS THE BIT POSITION:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
FIGURE 8 SHOWS THE GRAY-TO-BINARY AND BINARY-TO-GRAY
CODE CONVERSION IN OFFSET BINARY FORMAT. THE OUTPUT
FORMAT OF THE MAX12557 IS TWO'S-COMPLEMENT BINARY,
HENCE EACH MSB OF THE TWO'S-COMPLEMENT OUTPUT CODE
MUST BE INSERTED TO REFLECT TRUE OFFSET BINARY FORMAT.
D11
11
11
11
11
10
11
10
D13 D7 D3 D0
D11
110
D13 D7 D3 D0
D11
11
01
D13 D7 D3 D0
D11
D13 D7 D3 D0
D11
D13 D7 D3 D0
D11
D13 D7 D3 D0
D11
D13 D7 D3 D0
D11
Figure 8. Binary-to-Gray and Gray-to-Binary Code Conversion
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