s908az32ag2cfue Freescale Semiconductor, Inc, s908az32ag2cfue Datasheet - Page 230

• Manufacturer Part Number: s908az32ag2cfue
• Description: M68hc08 Microcontrollers 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Analog-To-Digital Converter (ADC-15)
21.3.2 Voltage Conversion
When the input voltage to the ADC equals V
signal to $FF (full scale). If the input voltage equals V
between V
voltages is not guaranteed. Avoid current injection on unused ADC inputs to prevent potential conversion
error.
21.3.3 Conversion Time
Conversion starts after a write to the ADSCR (ADC status control register, $0038), and requires between
16 and 17 ADC clock cycles to complete. Conversion time in terms of the number of bus cycles is a
function of ADICLK select, CGMXCLK frequency, bus frequency, and ADIV prescaler bits. For example,
with a CGMXCLK frequency of 4 MHz, bus frequency of 8 MHz, and fixed ADC clock frequency of 1 MHz,
230
REFH
INTERNAL
DATA BUS
AIEN
Input voltage should not exceed the analog supply voltages.
INTERRUPT
and V
LOGIC
READ DDRB/DDRB
WRITE DDRB/DDRD
WRITE PTB/PTD
READ PTB/PTD
COCO
SSA
BUS CLOCK
CONVERSION
COMPLETE
CGMXCLK
are a straight-line linear conversion. Conversion accuracy of all other input
RESET
Figure 21-1. ADC Block Diagram
MC68HC908AZ32A Data Sheet, Rev. 2
ADIV[2:0]
ADC DATA REGISTER
CLOCK
GENERATOR
REFH
DDRBx/DDRDx
ADC
PTBx/PTDx
ADC CLOCK
(see
NOTE
ADICLK
SSA,
25.1.6 ADC
the ADC converts it to $00. Input voltages
ADC VOLTAGE IN
ADCVIN
Characteristics), the ADC converts the
DISABLE
DISABLE
CHANNEL
SELECT
ADC CHANNEL x
Freescale Semiconductor
PTBx/PTDx
ADCH[4:0]