MC68HC16Z1 Datasheet, PDF (189/500 Pages) Freescale Semiconductor, Inc – M68HC16Z Series

Freescale Semiconductor, Inc.
8.2.2 Analog Reference Pins
Separate high (V_RH) and low (V_RL) analog reference voltages are connected to the an-
alog reference pins. The pins permit connection of regulated and filtered supplies that
allow the ADC to achieve its highest degree of accuracy.
8.2.3 Analog Supply Pins
Pins V_DDA and V_SSA supply power to analog circuitry associated with the RC DAC.
Other circuitry in the ADC is powered from the digital power bus (pins V_DDI and V_SSI).
Dedicated analog power supplies are necessary to isolate sensitive ADC circuitry from
noise on the digital power bus.
8.3 Programmer’s Model
The ADC module is mapped into 32 words of address space. Five words are control/
status registers, one word is digital port data, and 24 words provide access to the re-
sults of AD conversion (eight addresses for each type of converted data). Two words
are reserved for expansion.
The ADC module base address is determined by the value of the MM bit in the SIM
configuration register (SIMCR). The base address is normally $FFF700.
Internally, the ADC has both a differential data bus and a buffered IMB data bus. Reg-
isters not directly associated with conversion functions, such as the configuration reg-
ister, the test register, and the port data register, reside on the buffered bus, while
conversion registers and result registers reside on the differential bus.
Registers that reside on the buffered bus are updated immediately when written. How-
ever, writes to ADC control registers abort any conversion in progress.
8.4 ADC Bus Interface Unit
The ADC is designed to act as a slave device on the intermodule bus. The ADC bus
interface unit (ABIU) provides IMB bus cycle termination and synchronizes internal
ADC signals with IMB signals. The ABIU also manages data bus routing to accommo-
date the three conversion data formats, and controls the interface to the module differ-
ential data bus.
8.5 Special Operating Modes
Low-power stop mode and freeze mode are ADC operating modes associated with as-
sertion of IMB signals by other microcontroller modules or by external sources. These
modes are controlled by the values of bits in the ADC module configuration register
(ADCMCR).
8.5.1 Low-Power Stop Mode
When the STOP bit in ADCMCR is set, the IMB clock signal to the ADC is disabled.
This places the module in an idle state, and power consumption is minimized. The
ABIU does not shut down and ADC registers are still accessible. If a conversion is in
progress when STOP is set, it is aborted.
M68HC16 Z SERIES
ANALOG-TO-DIGITAL CONVERTER
USER’S MANUAL
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