MAXQ305J-0000 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAXQ305J-0000

Low-Voltage Microcontroller with Infrared Module

Maxim Integrated 

MAXQ305

Low-Voltage Microcontroller with Infrared Module

used to derive the 1.6V minimum crystal oscillator voltage

and the 1.4V (Q0.2V) core voltage.

To support flash program and erase operations, the

power conditioning block bumps the main charge-pump

voltage output up slightly and muxes the analog LDO

output to the flash supply pins to provide adequate

voltage levels to the flash to support programming. The

IR diode should not be activated when programming the

flash as the current capacity supplied by the main charge

pump well capacitor is used to supply the flash with

sufficient current in this mode. This makes flash program/

erase and IR diode operation mutually exclusive.

Memory

The MAXQ305 incorporates several memory types that

include the following:

• 80KB program flash memory

• 2KB SRAM data memory

• 6KB utility ROM

• Soft stack

Memory Protection

The optional memory-protection feature separates code

memory into three areas: system, user loader, and

user application. Code in the system area can be kept

confidential. Code in the user areas can be prevented

from reading and writing system code. The user loader

can also be protected from user application code.

Memory protection is implemented using privilege levels

for code. Each area has an associated privilege level.

RAM/ROM are assigned privilege levels as well. See

Table 1.

Stack Memory

The soft stack stores program return addresses (for

subroutine calls and interrupt handling) and other

general-purpose data. This soft stack is located in the

2KB SRAM data memory, which means that the SRAM

data memory must be shared between the soft stack

and general-purpose application data storage. However,

the location and size of the soft stack is determined by

the user, providing maximum flexibility when allocating

resources for a particular application. The stack is used

automatically by the processor when the CALL, RET, and

RETI instructions are executed and when an interrupt

is serviced. An application can also store and retrieve

values explicitly using the stack by means of the PUSH,

POP, and POPI instructions.

The SP pointer indicates the current top of the stack,

which initializes by default to the top of the SRAM data

memory. As values are pushed onto the stack, the SP

pointer decrements, which means that the stack grows

downward towards the bottom (lowest address) of the

data memory. Popping values off the stack causes the

SP pointer value to increase.

Utility ROM

The utility ROM is a 6KB block of internal ROM memory

located in program space beginning at address 8000h.

This ROM includes the following routines:

• In-system programming (bootstrap loader) using

JTAG interface

• In-circuit debugging routines using JTAG interface

• Production test routines (internal memory tests, mem-

ory loader, etc.) These are used for internal testing

only, and are generally of no use to the end-applica-

tion developer.

• User-callable routines for in-application flash pro-

gramming, buffer copying and fast table lookup. More

information on these routines can be found in the

MAXQ305 User’s Guide.

Following any reset, execution begins in the utility ROM

at address 8000h. At this point, unless loader mode or

test mode has been invoked (which requires special

programming via the JTAG interface), the utility ROM

always automatically jumps to location 0000h, which is

Table 1. Memory Areas and Associated Maximum Privilege Levels

AREA

System

User Loader

User Application

Utility ROM

Other (RAM)

PAGE ADDRESS

0 to ULDR-1

ULDR to UAPP-1

UAPP to top

N/A

N/A

MAXIMUM PRIVILEGE LEVEL

High

Medium

Low

High

Low

Maxim Integrated

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