MAXQ2000-RFX+ datasheet(28/39 Pages) MAXIM

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Low-Power LCD Microcontroller

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Power-On Reset

An internal power-on reset circuit enhances system reli-

ability. This circuit forces the device to perform a

power-on reset whenever a rising voltage on VDDIO

climbs above approximately 1.8V. At this point the fol-

lowing events occur:

• All registers and circuits enter their reset state

• The POR flag (WDCN.7) is set to indicate the source

of the reset

• The ring oscillator becomes the clock source and

• Code execution begins at location 8000h

Watchdog Timer Reset

The watchdog timer functions are described in the

MAXQ Family User’s Guide. Execution resumes at loca-

tion 8000h following a watchdog timer reset.

External System Reset

Asserting the external RESET pin low causes the device

to enter the reset state. The external reset functions as

described in the

MAXQ Family User’s Guide. Execution

resumes at location 8000h after the RESET pin is

released.

I/O Ports

The microcontroller uses the type C and type D bidirec-

tional I/O ports described in the

MAXQ Family User’s

Guide. The use of two port types allows for maximum

flexibility when interfacing to external peripherals. Each

port has eight independent, general-purpose I/O pins

and three configure/control registers. Many pins support

alternate functions such as timers or interrupts, which are

enabled, controlled, and monitored by dedicated periph-

eral registers. Using the alternate function automatically

converts the pin to that function.

Type-C port pins have Schmitt Trigger receivers and

full CMOS output drivers, and can support alternate

functions. The pin is either tri-stated or weak pullup

when defined as an input, dependent on the state of

the corresponding bit in the output register.

Type-D port pins have Schmitt Trigger receivers and

full CMOS output drivers, and can support alternate

functions. The pin is either tri-stated or weak pullup

when defined as an input, dependent on the state of

the corresponding bit in the output register. All type-D

pins also have interrupt capability.

MAXQ2000

PD.x

SF DIRECTION

SF ENABLE

PO.x

VDDIO

SF OUTPUT

VDDIO

WEAK

I/O PAD

PIN.x

INTERRUPT

FLAG

PI.x OR SF INPUT

EIES.x

TYPE-D PORT ONLY

DETECT

CIRCUIT

Figure 3. Type-C/D Port Pin Schematic

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