mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 222

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

10.8 Pin Considerations
10.8.1 Analog Reference Pins
10.8.2 Analog Power Pins
10-14
MOTOROLA
Result Data Format
right-justified format
Refer to APPENDIX D REGISTER SUMMARY for register mapping and configuration.
The ADC requires accurate, noise-free input signals for proper operation. The follow-
ing sections discuss the design of external circuitry to maximize ADC performance.
No A/D converter can be more accurate than its analog reference. Any noise in the
reference can result in at least that much error in a conversion. The reference for the
ADC, supplied by pins V
tain a noise-free, clean signal. In many cases, simple capacitive bypassing may suf-
fice. In extreme cases, inductors or ferrite beads may be necessary if noise or RF
energy is present. Series resistance is not advisable since there is an effective DC cur-
rent requirement from the reference voltage by the internal resistor string in the RC
DAC array. External resistance may introduce error in this architecture under certain
conditions. Any series devices in the filter network should contain a minimum amount
of DC resistance.
For accurate conversion results, the analog reference voltages must be within the lim-
its defined by V
The analog supply pins (V
ages (V
the analog input circuitry.
left-justified format
left-justified format
Unsigned
Unsigned
Signed
RH
and V
DDA
RL
Conversion result is unsigned right-justified data. Bits [9:0] are used for 10-bit resolution,
bits [7:0] are used for 8-bit conversion (bits [9:8] are zero). Bits [15:10] always return zero
when read.
Conversion result is signed left-justified data. Bits [15:6] are used for 10-bit resolution, bits
[15:8] are used for 8-bit conversion (bits [7:6] are zero). Although the ADC is unipolar, it
is assumed that the zero point is (V RH – V RL ) / 2 when this format is used. The value read
from the register is an offset two's-complement number; for positive input, bit 15 equals
zero, for negative input, bit 15 equals one. Bits [5:0] always return zero when read.
Conversion result is unsigned left-justified data. Bits [15:6] are used for 10-bit resolution,
bits [15:8] are used for 8-bit conversion (bits [7:6] are zero). Bits [5:0] always return zero
when read.
) and of the analog multiplexer inputs. Figure 10-4 is a diagram of
Freescale Semiconductor, Inc.
and V
Table 10-9 Result Register Formats
For More Information On This Product,
RH
ANALOG-TO-DIGITAL CONVERTER
DDA
SSA
and V
, as explained in the following subsection.
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and V
RL
, should be low-pass filtered from its source to ob-
SSA
) define the limits of the analog reference volt-
Description
MC68HC16Y3/916Y3
USER’S MANUAL