mc908jl16 Freescale Semiconductor, Inc, mc908jl16 Datasheet - Page 126

• Manufacturer Part Number: mc908jl16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Analog-to-Digital Converter (ADC)
A blocking mechanism prevents a new result from overwriting previous data in ADRH and ADRL if the
previous data is in the process of being read while in 10-bit mode (ADRH has been read but ADRL has
not). In this case the data transfer is blocked, COCO is not set, and the new result is lost. When a data
transfer is blocked, another conversion is initiated regardless of the state of ADCO (single or continuous
conversions enabled). If single conversions are enabled, this could result in several discarded
conversions and excess power consumption. To avoid this issue, the data registers must not be read after
initiating a single conversion until the conversion completes.
9.3.3.3 Aborting Conversions
Any conversion in progress will be aborted when:
When a conversion is aborted, the contents of the data registers, ADRH and ADRL, are not altered but
continue to be the values transferred after the completion of the last successful conversion. In the case
that the conversion was aborted by a reset, ADRH and ADRL return to their reset states.
Upon reset or when a conversion is otherwise aborted, the ADC10 module will enter a low power, inactive
state. In this state, all internal clocks and references are disabled. This state is entered asynchronously
and immediately upon aborting of a conversion.
9.3.3.4 Total Conversion Time
The total conversion time depends on many factors such as sample time, bus frequency, whether
ACLKEN is set, and synchronization time. The total conversion time is summarized in
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A write to ADCSC occurs (the current conversion will be aborted and a new conversion will be
initiated, if ADCH are not all 1s).
A write to ADCLK occurs.
The MCU is reset.
The MCU enters stop mode with ACLK not enabled.
8-Bit Mode (short sample — ADLSMP = 0):
8-Bit Mode (long sample — ADLSMP = 1):
10-Bit Mode (short sample — ADLSMP = 0):
10-Bit Mode (long sample — ADLSMP = 1):
Single or 1st continuous
Single or 1st continuous
Subsequent continuous (f
Single or 1st continuous
Single or 1st continuous
Subsequent continuous (f
Single or 1st continuous
Single or 1st continuous
Subsequent continuous (f
Single or 1st continuous
Single or 1st continuous
Subsequent continuous (f
Table 9-1. Total Conversion Time versus Control Conditions
Conversion Mode
Bus
Bus
Bus
Bus
≥ f
≥ f
≥ f
≥ f
MC68HC908JL16 Data Sheet, Rev. 1.1
ADCK
ADCK
ADCK
ADCK
)
)
)
)
ACLKEN
X
X
X
X
0
1
0
1
0
1
0
1
38 ADCK + 3 bus clock + 5 µs
21 ADCK + 3 bus clock + 5 µs
41 ADCK + 3 bus clock + 5 µs
18 ADCK + 3 bus clock + 5 µs
Maximum Conversion Time
18 ADCK + 3 bus clock
38 ADCK + 3 bus clock
21 ADCK + 3 bus clock
41 ADCK + 3 bus clock
16 ADCK
36 ADCK
19 ADCK
39 ADCK
Freescale Semiconductor
Table
9-1.