ADC1 data are 32 bits in a twos complement format that represents positive and negative values, and are output starting with the most significant bit first (ADC1[31]). The data are scaled so that VIN = 0 V results in ideal code value of 00000000h; see Table 9-19 for other ideal code values. Some applications require reduction of the 32-bit data to 24-bit data in order to provide compatibility to 24-bit systems. This reduction is done by simple truncation (or rounding) of the 32-bit data to 24 bits. See Figure 9-46 for the ADC1 data byte field.
Table 9-19 ADC1 and ADC2 Output Codes
INPUT SIGNAL (V)(1) |
ADC1 OUTPUT CODE (32 Bits) (2) |
ADC2 OUTPUT CODE (24 Bits) (2) |
≥ VREF / Gain · (2N–1 - 1) /
2N–1 |
7FFFFFFFh |
7FFFFFh |
VREF / (Gain · 2N–1 ) |
00000001h |
000001h |
0 |
00000000h |
000000h |
–VREF / (Gain · 2N–1 ) |
FFFFFFFFh |
FFFFFFh |
≤ –VREF / Gain |
80000000h |
800000h |
(1) N = 32 (ADC1), N = 24 (ADC2)
(2) Ideal output code, excluding effects of ADC noise, offset, gain and linearity errors.
Figure 9-46 ADC1 Data Field, Four
Bytes - 32 Bits31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 |
ADC1[31:24] |
R-0 |
23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 |
ADC1[23:16] |
R-0 |
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
ADC1[15:8] |
R-0 |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
ADC1[7:0] |
R-0 |
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset |
ADC2 data are 24 bits in a twos complement data format that represents positive and negative code values, and are output starting with the most significant bit first (ADC2[23]). The data are scaled so that a zero-voltage input results in an ideal code value of 000000h; see Table 9-19 for other ideal code values. See Figure 9-47 for the ADC2 data-byte field.
Figure 9-47 ADC2 Data Field, Three
Bytes - 24 Bits23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 |
ADC2[23:16] |
R-0 |
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
ADC2[15:8] |
R-0 |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
ADC2[7:0] |
R-0 |
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset |