TLC8044 Datasheet, PDF (22/32 Pages) Texas Instruments – 12-BIT ANALOG-TO-DIGITAL INTERFACE FOR CHARGE-COUPLED DEVICE IMAGE SENSORS FOR SCANNERS

TLC8044
12-BIT ANALOG-TO-DIGITAL INTERFACE FOR
CHARGE-COUPLED DEVICE IMAGE SENSORS FOR SCANNERS
SLAS128 – JUNE 1997
PRINCIPLES OF OPERATION
effect of image processing on ADC output (continued)
In Table 4, example 2 shows how the half range ADCOP value (2048) is affected by adding dc restoration (value
128). This value is added directly to the ADCOP value. All other parameters are default, so this result passes
directly to the OP0–OP11 output. Inserting the values in the formula gives:
OP0–OP11 = (((2048 + 128 + (0 × 1)) × 1) + (0.5 × 0)) × 1
In Table 4, example 9 shows the effect of internal scaling (POSCL) on the pixel offset compensation (POC). The
value 01 on POSCL indicates a scaling factor of 0.5 (refer to Table 5, setup register 2). The POC value of 128
is multiplied by 0.5. The result is added to the ADC output. Defaults have been used on all other stages, so the
resulting value of 2048 is directly output on OP0–OP11. Examples 10 and 11 show the effect of different scaling
factors. Inserting the values in the formula gives:
OP0–OP11 = (((2048 + 0 + (128 × 0.5)) × 1) + (0.5 × 0)) × 1
Table 4. Examples of Image Processing on ADC Output
PARAMETER
Range
Default
Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Example 7
Example 8
Example 9
Example 10
Example 11
ADCOP
0 to 4095
2048
2048
2048
2048
2048
2048
2048
2048
2048
2048
2048
DCREST
–2048 to 2047
0
0
128
0
0
–64
0
0
–64
0
0
0
POC
–2048 to 2047
0
0
0
–256
0
128
0
0
128
128
128
128
POSCL
00
00
00
00
00
00
00
00
00
01
10
11
PCS
0 to 4095
1024
1024
1024
1024
512
1536
1024
1024
512
1024
1024
1024
GLOBAL OFFSET
–32768 to 32767
0
0
0
0
0
0
1024
0
1024
0
0
0
GLOBAL GAIN
0 to 65536
32768
32768
32768
32768
32768
32768
32768
16384
16384
32768
32768
32768
OP0–OP11
0 to 4095
2048
2176
1792
1024
3168
2560
1024
784
2112
2080
2064
NOTE:
OP0–OP11 = (((ADCOP + DCREST + (POC × POSCL)) × PSC) + (0.5 × Global Offset)) × Global Gain
where:
ADCOP
12-bit output of the ADC
DCREST
2s complement 12-bit number source directly from the DC restore registers
POC
2s complement 12-bit number source directly from the POC bus or registers
POSCL
scaling factor as defined in Table 5 setup register 2
PSC
12-bit unsigned number sourced from the PSC bus or register and divided by 1024
Global Offset 16-bit 2s complement number sourced directly form the global offset adjust registers
Global Gain 16-bit unsigned number sourced from the global gain register and divided by 32768
OP0–OP11 12-bit result of the image processing that is output from the device on the bus OP0–OP15
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