MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 320

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Analog-to-Digital Converter (ADC)
19.4.2 Voltage Conversion
19.4.3 Conversion Time
Advance Information
320
NOTE:
NOTE:
overrides the port I/O logic by forcing that pin as input to the ADC. The
remaining ADC channels/port pins are controlled by the port I/O logic
and can be used as general-purpose I/O. Writes to the port register or
DDR will not have any affect on the port pin that is selected by the ADC.
Read of a port pin which is in use by the ADC will return a logic 0 if the
corresponding DDR bit is at logic 0. If the DDR bit is at logic 1, the value
in the port data latch is read.
Do not use ADC channel ATD14 when using the PTD6/ATD14/TCLK pin
as the clock input for the TIM.
When the input voltage to the ADC equals V
Characteristics), the ADC converts the signal to $FF (full scale). If the
input voltage equals V
voltages between V
conversion. All other input voltages will result in $FF if greater than
V
Input voltage should not exceed the analog supply voltages.
Sixteen ADC internal clocks are required to perform one conversion. The
ADC starts a conversion on the first rising edge of the ADC internal clock
immediately following a write to the ADSCR. If the ADC internal clock is
selected to run at 1 MHz, then one conversion will take 16 s to
complete. But since the ADC can run almost completely asynchronously
to the bus clock, (for example, the ADC is configured to derive its internal
clock from CGMXCLK and the bus clock is being derived from the PLL
within the CGM [CGMOUT]), this 16 s conversion can take up to 17 s
to complete. This worst-case could occur if the write to the ADSCR
happened directly after the rising edge of the ADC internal clock causing
REFH
and $00 if less than V
Analog-to-Digital Converter (ADC)
REFH
SSA
and V
/V
REFL,
SSA
SSA
/V
the ADC converts it to $00. Input
REFL
/V
REFL
.
are a straight-line linear
REFH
MC68HC708AS48
(see
21.7 ADC
MOTOROLA
—
Rev. 4.0