MC68HC705X32CFU Freescale Semiconductor, MC68HC705X32CFU Datasheet - Page 129

• Manufacturer Part Number: MC68HC705X32CFU
• Manufacturer: Freescale Semiconductor

Specifications of MC68HC705X32CFU

• Cpu Family: HC05
• Device Core Size: 8b
• Frequency (max): 4MHz
• Interface Type: SCI
• Program Memory Type: EPROM
• Program Memory Size: 32KB
• Total Internal Ram Size: 528Byte
• # I/os (max): 32
• Number Of Timers - General Purpose: 1
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• On-chip Adc: 8-chx8-bit
• Instruction Set Architecture: CISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 64
• Package Type: PQFP
• Lead Free Status / Rohs Status: Supplier Unconfirmed

Freescale Semiconductor, Inc.
9
ANALOG TO DIGITAL CONVERTER
The analog to digital converter system consists of a single 8-bit successive approximation
converter and a sixteen channel multiplexer. Eight of the channels are connected to the
PD0/AN0 – PD7/AN7 pins of the MC68HC05X16 and the other eight channels are dedicated to
internal reference points for test functions. The channel input pins do not have any internal output
driver circuitry connected to them because such circuitry would load the analog input signals due
to output buffer leakage current. There is one 8-bit result data register (address $08) and one 8-bit
status/control register (address $09).
The A/D converter is ratiometric and two dedicated pins, VRH and VRL, are used to supply the
reference voltage levels for all analog inputs. These pins are used in preference to the system
power supply lines because any voltage drops in the bonding wires of the heavily loaded supply
pins could degrade the accuracy of the A/D conversion. An input voltage equal to or greater than
V
converts to $FF (full scale) with no overflow indication and an input voltage equal to V
RH
RL
converts to $00.
The A/D converter can operate from either the bus clock or an internal RC type oscillator. The
9
internal RC type oscillator is activated by the ADRC bit in the A/D status/control register (ADSTAT)
and can be used to give a sufficiently high clock rate to the A/D converter when the bus speed is too
low to provide accurate results. When the A/D converter is not being used it can be disconnected,
by clearing the ADON bit in the ADSTAT register, in order to save power (see
Section
9.2.3).
For further information on A/D converter operation please refer to the M68HC11 Reference
Manual — M68HC11RM/AD.
9.1
A/D converter operation
The A/D converter consists of an analog multiplexer, an 8-bit digital to analog converter capacitor
array, a comparator and a successive approximation register (SAR) (see
Figure
9-1).
There are eleven options that can be selected by the multiplexer; AN0–AN7, VRH, (VRH+VRL)/2
or VRL. Selection is done via the CHx bits in the ADSTAT register (see
Section
9.2.3). AN0–AN7
are the only input points for A/D conversion operations; the others are reference points that can be
used for test purposes.
MC68HC05X16
ANALOG TO DIGITAL CONVERTER
For More Information On This Product,
9-1
Go to: www.freescale.com