maxq3212-emx+ Maxim Integrated Products, Inc., maxq3212-emx+ Datasheet - Page 9

• Manufacturer Part Number: maxq3212-emx+
• Description: Maxq3212 Microcontroller With Analog Comparator And Led Driver
• Manufacturer: Maxim Integrated Products, Inc.

A 16-bit-wide internal stack provides storage for pro-
gram return addresses and general-purpose use. The
stack is used automatically by the processor when the
CALL, RET, and RETI instructions are executed and
interrupts serviced. The PUSH, POP, and POPI instruc-
tions can also be used explicitly to store and retrieve
data to/from the stack. For the MAXQ3212, the stack is
four levels deep.
On reset, the stack pointer, SP, initializes to the top of
the stack (03h). The CALL, PUSH, and interrupt-vector-
ing operations increment SP, then store a value at the
stack location pointed to by SP. The RET, RETI, POP,
and POPI operations retrieve the value at the stack
location pointed to by SP, and then decrement SP.
The utility ROM is a block of internal memory that starts
at address 8000h. The utility ROM consists of subrou-
tines that can be called from application software.
These include:
• In-system programming (bootloader) over JTAG
• In-circuit debug routines
• Test routines (internal memory tests, memory loader,
• User-callable routines for in-application EEPROM
Routines within the utility ROM are user-accessible and
can be called as subroutines by the application soft-
ware. More information on the utility ROM contents is
contained in the user’s guide for this device.
Some applications require protection against unautho-
rized viewing of program code memory. For these
applications, access to in-system programming or in-
circuit debugging functions is prohibited until a pass-
word has been supplied. The password is defined as
the 16 words of physical program memory at address-
es x0010h to x001Fh.
A single Password Lock (PWL) bit is implemented in
the SC register. When the PWL is set to one (power-on
reset default), the password is required to access the
utility ROM, including in-circuit debug and in-system
programming routines that allow reading or writing of
internal memory. When PWL is cleared to zero, these
interface
etc.)
programming and fast table lookup
Microcontroller with Analog Comparator
Stack Memory
_____________________________________________________________________
Utility ROM
utilities are fully accessible without the password. The
password is automatically set to all zeros following a
mass erase. An additional Code Lock bit set from the
bootloader prevents any access to the device, even
through the password. The device must be erased by
the mass erase operation to clear the Code Lock bit
before the device can be reprogrammed.
The microcontroller’s EEPROM can be programmed by
two different methods: in-system programming and in-
application programming. Both methods afford great
flexibility in system design as well as reduce the life-
cycle cost of the embedded system. In-system pro-
gramming can be password protected to prevent
unauthorized access to code memory.
An internal bootloader allows the device to be reloaded
over a simple JTAG interface. As a result, system soft-
ware can be upgraded in-system, eliminating the need
for a costly hardware retrofit when software updates are
required. Remote software uploads are possible that
enable physically inaccessible applications to be fre-
quently updated. The interface hardware can be a JTAG
connection to another microcontroller, or a connection to
a PC serial port using a serial-to-JTAG converter. If in-
system programmability is not required, a commercial
gang programmer can be used for mass programming.
Activating the JTAG interface and sending the system
programming instruction invokes the bootloader.
Setting the SPE bit to 1 during reset through the JTAG
interface executes the bootloader-mode program that
resides in the utility ROM. When programming is com-
plete, the bootloader can clear the SPE bit and reset
the device, allowing the device to bypass the utility
ROM and begin execution of the application software.
Optionally, the bootloader can be invoked by the appli-
cation code.
The following bootloader functions are supported:
• Load
• Dump
• CRC
• Verify
• Erase
and LED Driver
In-System Programming
Programming
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