MAXQ2000-RFX+ datasheet(31/39 Pages) MAXIM

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Low-Power LCD Microcontroller

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In-Circuit Debug

Embedded debugging capability is available through

the JTAG-compatible Test Access Port. Embedded

debug hardware and embedded ROM firmware pro-

vide in-circuit debugging capability to the user applica-

tion, eliminating the need for an expensive in-circuit

emulator. Figure 4 shows a block diagram of the in-cir-

cuit debugger. The in-circuit debug features include:

• a hardware debug engine,

• a set of registers able to set breakpoints on register,

code, or data accesses, and

• a set of debug service routines stored in the utility

ROM.

The embedded hardware debug engine is an indepen-

dent hardware block in the microcontroller. The debug

engine can monitor internal activities and interact with

selected internal registers while the CPU is executing

user code. Collectively, the hardware and software fea-

tures allow two basic modes of in-circuit debugging:

• Background mode allows the host to configure and set

up the in-circuit debugger while the CPU continues to

execute the application software at full speed. Debug

mode can be invoked from background mode.

• Debug mode allows the debug engine to take control

of the CPU, providing read/write access to internal reg-

isters and memory, and single-step trace operation.

LCD Controller

The MAXQ2000 microcontroller incorporates an LCD

controller that interfaces to common low-voltage dis-

plays. By incorporating the LCD controller into the

microcontroller, the design requires only an LCD glass

rather than a considerably more expensive LCD mod-

ule. Every character in an LCD glass is composed of

one or more segments, each of which is activated by

selecting the appropriate segment and common signal.

The microcontroller can multiplex combinations of up to

33 segment (SEG0–SEG32) outputs and four common

signal outputs (COM0–COM3). Unused segment out-

puts can be used as general-purpose port pins.

The segments are easily addressed by writing to dedi-

cated display memory. Once the LCD controller set-

tings and display memory have been initialized, the

17-byte display memory is periodically scanned, and

the segment and common signals are generated auto-

matically at the selected display frequency. No addi-

tional processor overhead is required while the LCD

controller is running. Unused display memory can be

used for general-purpose storage.

The design is further simplified and cost-reduced by

the inclusion of software-adjustable internal voltage

dividers to control display contrast, using either VDDIO

or an external voltage. If desired, contrast can also be

controlled with an external resistance. The features of

the LCD controller include the following:

• Automatic LCD segment and common-drive signal

generation

• Four display modes supported:

Static (COM0)

1/2 duty multiplexed with 1/2 bias voltages (COM0,

COM1)

1/3 duty multiplexed with 1/3 bias voltages (COM0,

COM1, COM2)

1/4 duty multiplexed with 1/3 bias voltages (COM0,

COM1, COM2, COM3)

• Up to 36 segment outputs and four common-signal

outputs

• 17 bytes (136 bits) of display memory

• Flexible LCD clock source, selectable from 32kHz or

HFClk / 128

• Adjustable frame frequency

• Internal voltage-divider resistors eliminate require-

ment for external components

• Internal adjustable resistor allows contrast adjustment

without external components

TAP

CONTROLLER

CPU

DEBUG

ENGINE

DEBUG

SERVICE

ROUTINES

(UTILITY ROM)

TMS

TCK

TDI

TDO

CONTROL

BREAKPOINT

ADDRESS

DATA

MAXQ2000

Figure 4. In-Circuit Debugger

MAXQ2000-RFX+ Datasheet(PDF) 31 Page - Maxim Integrated Products

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