Datasheet

Every function of the DOP module can be selected indi-
vidually (DAC, PWM, or op amp), or two out of the three
functions of the DOP module can be selected at the same
time (PWM and op amp, or DAC and PWM, or DAC and
op amp), as there are only two output pins for the mod-
ule, OUTnSM and OUTnLG. The various configuration
options for the DOP are shown in Table 21. The PWRDAC
and PWROP bits are in the power-on control register
(address = 31h), and the remaining bits are in the DOP
registers. See Tables 21 through 27.
Timer Module
The timer module (Figure 6) comprises a 12-bit counter,
a 4-bit prescalar, and control and configuration registers.
When the timer is enabled and initiated, the system mas-
ter clock, MCLK, is prescaled by the divisor set by PS[3:0]
in the TMR_Config register and the result applied to the
12- bit upcounter. When the counter value matches the
timeout value TO[11:0] in register TMR_Config, bit TMDN
is set to 1. The CPU can poll the timer done bit TMDN to
check its status.
The timer module provides a feature that enables the
CPU to be put into a low-power halt mode for the dura-
tion of the timer interval. Setting the ENAHALT bit in the
TMR_Control register while starting the timer (setting the
timer enable bit TMEN to 1), or while the timer is already
enabled and counting halts the CPU at the present
instruction until the TMDN bit becomes set by the counter.
The CPU commences execution with the next instruction.
All CPU registers and ports are fully static and retain all
data during the elapsed time interval.
The time interval between TMEN being set to 1, and
TMDN being set to 1 can be computed as follows:
Time Interval = (2 / f
OSC
) x {(prescale value N)
x (timeout value TO[11:0]) + 1.5}
The maximum time interval given fOSC = 4MHz clock is
786ms.
Power Control
The power to various subcircuits in the MAX1464 can
be turned on and off by CPU control and by the serial
interface. Unused subcircuits and modules can be turned
off to reduce power consumption. The default state after
power-on is all subcircuits and modules powered off. This
enables low-power embedded systems to turn on only the
needed modules after exiting a low-power CPU halt timer
interval. Modules can be turned on and off as needed;
however, care must be exercised to allow for module ini-
tialization and settling prior to use.
Oscillator Control
The MAX1464 has a fully integrated oscillator with a
nominal 4MHz frequency. An external clock source can be
used when the clock-select pin CKSEL = 0, operating all
internal timing functions. CKIO can also be configured as
an output source of the internal oscillator clock.
GPIO Module
The MAX1464 contains two general-purpose digital input/
output (GPIO) modules, GPIO1 and GPIO2, which can
be written and read by CPU control and by the serial
interface. These two I/O pins operate independently of
each other. They can be configured as inputs, outputs, or
one input and one output. When configured as an input,
there are two modes of sensing digital inputs; as a voltage
or logic level, or as an edge detector. In edge-detector
mode, either a rising or falling edge can be selected for
detection. A bit is set in the GPIO control register upon
detection of the selected edge.
The GPIO pins have nominal 100kΩ pulldown resistors to
V
SS
as in Figure 6. Pulldown resistors provide a low logic
level when the pin is unconnected. The GPIO may also
serve as an input pin and its state is read from the GPIO
control register (Tables 28 and 29). When using the GPIO
pin as a general-purpose output, its output state is defined
by writing to the GPIO control register.
The GPIOn pins can be configured as an alert output that
goes low or high whenever a fault condition happens,
e.g., remote sensor line disconnection, overflow condi-
tions in the CPU program execution, etc.
All input and output control for the GPIO1 and GPIO2
pins are contained in GPIO1_Control (address = 40h)
and GPIO2_Control (address = 41h), respectively. Figure
7 shows the GPIO1 and GPIO2 modules.
Serial Interface Timing and Operation
The MAX1464 serial interface is a high-speed asynchro-
nous data input and output communication port, providing
access to internal registers for calibration of embedded
control sensor systems. All the FLASH memory is read
Figure 6. Timer Module
20hTMR_Control
21hTMR_Config
PRESCALER
12-BIT COUNTER
TIMEOUT VALUE
MCLK
MAX1464 Low-Power, Low-Noise Multichannel
Sensor Signal Processor
www.maximintegrated.com
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