MAXQ2000-RFX+ datasheet(29/39 Pages) MAXIM

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Low-Power LCD Microcontroller

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High-Speed Hardware Multiplier

The hardware multiplier module performs high-speed

multiply, square, and accumulate operations, and can

complete a 16-bit x 16-bit multiply-and-accumulate

operation in a single cycle. The hardware multiplier

consists of two 16-bit parallel-load operand registers

(MA, MB), an accumulator that is formed by up to three

16-bit parallel registers (MC2, MC1, and MC0), and a

status/control register (MCNT). Loading the registers

can automatically initiate the operation, saving time on

repetitive calculations. The accumulate function of the

hardware multiplier is an essential element of digital fil-

tering, signal processing, and PID control systems.

The hardware multiplier module supports the following

operations:

• Multiply unsigned (16 bit x 16 bit)

• Multiply signed (16 bit x 16 bit)

• Multiply-Accumulate unsigned (16 bit x 16 bit)

• Multiply-Accumulate signed (16 bit x 16 bit)

• Square unsigned (16 bit)

• Square signed (16 bit)

• Square-Accumulate unsigned (16 bit)

• Square-Accumulate signed (16 bit)

Real-Time Clock

A binary real-time clock keeps the time of day in

absolute seconds with 1/256-second resolution. The

32-bit second counter can count up to approximately

136 years and be translated to calendar format by the

application software. A time-of-day alarm and indepen-

dent subsecond alarm can cause an interrupt, or wake

the device from Stop mode.

The independent subsecond alarm runs from the same

RTC, and allows the application to perform periodic

interrupts up to ones with a granularity of approximately

3.9ms. This creates an additional timer that can be

used to measure long periods without performance

degradations. Traditionally, long time periods have

been measured using multiple interrupts from shorter

programmable timers. Each timer interrupt required

servicing, with each accompanying interruption slowing

system operation. By using the RTC subsecond timer

as a long-period timer, only one interrupt is needed,

eliminating the performance hit associated with using a

shorter timer.

An internal crystal oscillator clocks the RTC using inte-

grated 6pF load capacitors, and give the best perfor-

mance when mated with a 32.768kHz crystal rated for a

6pF load. No external load capacitors are required.

Higher accuracy can be obtained by supplying an exter-

nal clock source to the RTC. The frequency accuracy of

a crystal-based oscillator circuit is dependent upon crys-

tal accuracy, the match between the crystal and the

oscillator capacitor load, ambient temperature, etc. An

error of 20ppm is equivalent to approximately 1 minute

per month.

Programmable Timers

The microcontroller incorporates three 16-bit program-

mable instances of the Timer 2 peripheral, denoted

TR2A, TR2B, and TR2C. These timers can be used in

counter/timer/capture/compare/PWM functions, allow-

ing precise control of internal and external events.

Timer 2 supports optional single-shot, external gating,

and polarity control options.

Timer 2

The Timer 2 peripheral includes the following:

• 16-bit autoreload timer/counter

• 16-bit capture

• 16-bit counter

• 8-bit capture and 8-bit timer

• 8-bit counter and 8-bit timer

Watchdog Timer

An internal watchdog timer greatly increases system

reliability. The timer resets the device if software execu-

tion is disturbed. The watchdog timer is a free-running

counter designed to be periodically reset by the appli-

cation software. If software is operating correctly, the

counter will be periodically reset and never reach its

maximum count. However, if software operation is inter-

rupted, the timer does not reset, triggering a system

reset and optionally a watchdog timer interrupt. This

protects the system against electrical noise or electro-

static discharge (ESD) upsets that could cause uncon-

trolled processor operation. The internal watchdog

timer is an upgrade to older designs with external

watchdog devices, reducing system cost and simulta-

neously increasing reliability.

MAXQ2000-RFX+ Datasheet(PDF) 29 Page - Maxim Integrated Products

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