MC68HC05SR3D Datasheet, PDF (51/96 Pages) Freescale Semiconductor, Inc – Microcontrollers

7
ANALOG TO DIGITAL CONVERTER
The analog to digital converter system consists of a single 8-bit successive approximation
converter and an 8-channel analog multiplexer. Four of the channels are available for analog
inputs, and the other four channels are dedicated to internal test functions. There is one 8-bit ADC
Data Register ($0F) and one 8-bit ADC Status and Control register ($0E). The reference supply,
V_RL and V_RH for the converter uses two input pins (shared with PD4 and PD5) instead of the power
supply lines, because drops caused by loading in the power supply lines would degrade the
accuracy of the analog to digital conversion. An internal RC oscillator is available if the bus speed
is low enough to degrade the ADC accuracy. An ADON bit allows the ADC to be switched off to
reduce power consumption, which is particularly useful in the Wait mode.
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AN0
AN1
AN2
AN3
V_RH
V_RL
(V_RH + V_RL)/4
(V_RH + V_RL)/2
8-bit capacitive DAC
with sample and hold
VRH
VRL
Sucrceegsisstiever _{aanpdprcooxnimtroaltion}
Result
8
ADC Status and Control Register ($0E)
CH0 CH1 CH2
ADON ADRC COCO
ADC Data Register ($0F)
Figure 7-1 ADC Converter Block Diagram
MC68HC05SR3
ANALOG TO DIGITAL CONVERTER
TPG
Freescale
7-1