MAX1463 Datasheet, PDF (14/49 Pages) Maxim Integrated Products – Low-Power Two-Channel Sensor Signal Processor

Low-Power Two-Channel Sensor
Signal Processor
SERIAL INTERFACE
P0
P1
P2
CPU
P1
P3
P4
P5
P6
P7
P8
PA
PB
PC
PD
PE
PF
CPU PORTS
R0 POINTER (P)
R1 ACCUMULATOR (A)
R2
R3 MULTIPLICAND (N)
R4 MULTIPLIER (M)
R5 INDEX (I)
R6
R7
R8
R9
RA
RB
RC
RD
RE
RF
CPU REGISTERS
INSTRUCTION
ADDRESS
FLASH MEMORY
(4kB)
FLASH DATA
Figure 3. CPU Architecture
The CPU registers and ports are implemented in
volatile, static memory. There are several registers con-
tained in various peripheral modules that provide mod-
ule configuration settings, control functions, and data.
These module registers are accessible through an indi-
rect addressing scheme as described in detail in the
CPU Registers, CPU Ports, and Modules sections.
Figure 3 shows the CPU architecture.
CPU Registers
The MAX1463 incorporates a CPU with 16 internal reg-
isters. All of the CPU registers have a 16-bit data word
width. Five of the 16 registers have predefined function-
al operation dependent on the instruction being execut-
ed. The remaining registers are general purpose.
The CPU registers are embedded in the CPU itself and
are not all directly accessible by the serial interface.
The accumulator register (A), the pointer register (P),
and the instruction (FLASH data) can be read through
the serial interface when the CPU is halted. This
enables a single-step mode of code execution to ease
code writing and debugging. A special program
instruction sequence is required to observe the other
CPU registers. Table 1 lists the CPU registers.
CPU Ports
The MAX1463 incorporates 16 CPU ports that are directly
accessible by the serial interface. All the CPU ports have
a 16-bit data-word width. The contents of the ports can
be read and written by transferring data to and from the
accumulator register (A) using the RDX and WRX instruc-
tions. No other CPU instructions act on the CPU ports.
Three CPU ports PD, PE, and PF have uniquely defined
operation for reading and writing data to and from the
peripheral modules. All CPU ports are static and volatile.
Modules
The MAX1463 modules are the functional blocks used to
process analog and digital signals to and from the CPU.
Each module is addressed through CPU ports PD, PE,
and PF, as described in the CPU Ports section. All mod-
ules use static, volatile registers for data retention. There
are three types of module registers: configuration, data,
and control. They are used to put a module into a partic-
ular mode of operation. Configuration registers hold con-
figuration bits that control static settings such as PGA
gain, coarse offset, etc. Data registers hold input data
such as DAC and PWM input words or output data such
as the result of an ADC conversion. Control registers are
used to initiate a process (such as an ADC conversion or
a timer) or to turn modules on and off (such as op amps,
DAC outputs, PWM outputs, etc.)
ADC Module
The ADC module (Figure 4) contains a 9-bit to 16-bit
sigma-delta converter with multiplexed differential and
single-ended signal inputs, a CO DAC, four reference
voltage inputs, two differential or four single-ended
external inputs, and 15 single-ended internal voltages
for measurement. The ADC output data is 16-bit two’s
complement format. The conversion channel, modes,
and reference sources are all set in ADC configuration
registers. The conversion time is a function of the
selected resolution and ADC clock frequency. The CPU
can be programmed to convert any of the inputs and
the internal temperature sensor in any desired
sequence. For example, the differential inputs may be
converted many times and conversions of temperature
performed less frequently.
The ADC uses the internal 1.25V bandgap reference
(V_BG) when converting the temperature input.
For any other conversions, the ADC reference can be
selected as V_DD for conversions ratiometric to the
power supply, VREF pin for conversions relative to an
external voltage, and VBGx4, which is an internally
generated “pseudo” 5.0V reference source. The ADC
voltage reference is also used by the CO DAC to main-
tain a signal conversion that is ratiometric to the select-
ed reference source.
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