MAXQ2000 Maxim, MAXQ2000 Datasheet - Page 28

• Manufacturer Part Number: MAXQ2000
• Description: The MAXQ2000 microcontroller is a low-power, 16-bit device that incorporates a liquid-crystal display (LCD) interface that can drive up to 100 (-RBX/-RBX+) or 132 (-RAX/-RAX+/-RFX/-RFX+) segments
• Manufacturer: Maxim

Low-Power LCD Microcontroller
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 V
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
• The ring oscillator becomes the clock source and
• Code execution begins at location 8000h
The watchdog timer functions are described in the
MAXQ Family User’s Guide . Execution resumes at loca-
tion 8000h following a watchdog timer 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.
Figure 3. Type-C/D Port Pin Schematic
28
of the reset
____________________________________________________________________
PI.x OR SF INPUT
SF DIRECTION
FLAG
SF OUTPUT
SF ENABLE
PD.x
PO.x
Watchdog Timer Reset
External System Reset
INTERRUPT
FLAG
Power-On Reset
CIRCUIT
DETECT
EIES.x
DDIO
TYPE-D PORT ONLY
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
I/O PAD
V
DDIO
V
WEAK
DDIO
PIN.x
I/O Ports