Z86C83 Zilog., Z86C83 Datasheet - Page 28

• Manufacturer Part Number: Z86C83
• Description: Z8 MCU MICROCONTROLLERS
• Manufacturer: Zilog.

Z86C83/C84
Z8
Analog-to-Digital Converter
The Analog-to-Digital (ADC) is an 8-bit half flash converter
that uses two reference resistor ladders for its upper 4 bits
(MSBs) and lower 4 bits (LSBs) conversion. Two reference
voltage pins, AV
reference voltage supplies. During the sampling period
from one of the eight channel inputs, the converter is also
being auto-zeroed before starting the conversion. The
conversion time is dependent on the internal clock
frequency. The minimum conversion time is 35 X
SCLK(see Figure 22).
The ADC is controlled by the Z8
(two Control and one Result) are mapped into the
Extended Register File. A conversion can be initiated by
writing to the ADC Control Register 0 after the ADC
Control Register 1 is configured.
The start command is implemented in such a way as to
begin a conversion at any time, if a conversion is in
progress and a new start command is received, then the
conversion in progress will be aborted and a new
conversion will be initiated. This allows the programmed
values to be changed without affecting a conversion-in-
28
®
MCU Microcontrollers
8 8
8
CC
8
and A
Control
Control
Result
ADR1
ADC1
ADC0
Reg.
Reg.
Reg.
A/D
A/D
A/D
GND
, are provided for external
®
and its three registers
Converter
Start
EXT
Figure 22. ADC Architecture
Selected
Channel
Converter
A/D
Vref +
Vref -
GND
Vcc
progress. The new values will take effect only after a new
start command is received.
The ADC can be disabled (for low power) or enabled by a
Control Register bit.
Though the ADC will function for a smaller input voltage
and voltage reference, the noise and offsets remain
constant over the specified electrical range. The errors of
the converter will increase and the conversion time may
also take slightly longer due to smaller input signals.
ADC Calibration Offset
Specially matched resistors are program-enabled to allow
35.0 percent or 50 percent offset from A
selectively enable these resistors to offset the A
percent (2.5V to 5V) or 50 percent (1.75V to 5V) thereby
allowing the 8-bit ADC across a narrower voltage range.
This will allow significant resolution improvement within
the reduced voltage range.
Note: The AV
must be the same value as GND.
Sample
Hold
and
CC
ADC Register
must be the same value as V
D4, D5
9
4
Calibration Offset
AV
A
GND
CC
DS96DZ80203
GND
. They may
CC
GND
and A
by 35.0
GND