MAXQ622G-0000 MAXIM [Maxim Integrated Products], MAXQ622G-0000 Datasheet - Page 27

• Manufacturer Part Number: MAXQ622G-0000
• Description: 16-Bit Microcontrollers with Infrared Module and Optional USB
• Manufacturer: MAXIM [Maxim Integrated Products]

pin to GND. The clock source should be driven through
a CMOS driver. If the clock driver is a TTL gate, its output
must be connected to V
ensure a satisfactory logic level for active clock pulses.
To minimize system noise on the clock circuitry, the
external clock source must meet the maximum rise and
fall times and the minimum high and low times specified
for the clock source. The external noise can affect the
clock generation circuit if these parameters do not meet
the specification.
Noise at HFXIN and HFXOUT can adversely affect on-
chip clock timing. It is good design practice to place
the crystal and capacitors as near the oscillator circuitry
as possible with a direct short trace. The typical values
of external capacitors vary with the type of crystal to be
used.
The ROM loader loads program memory and config-
ures loader-specific configuration features. To increase
the security of the system, the loader denies access to
the system, user loader, or user-application memories
unless an area-specific password is provided.
An internal bootstrap loader allows reloading over a
simple JTAG interface. As a result, software can be
upgraded in-system, eliminating the need for a costly
hardware retrofit when updates are required. Remote
software uploads are possible that enable physically
inaccessible applications to be frequently updated. The
interface hardware can be a JTAG connection to another
microcontroller, or a connection to a PC serial port using
a USB-to-JTAG converter such as the MAXQUSBJTAG-
KIT#, available from Maxim. If in-system programmabil-
ity is not required, a commercial gang programmer can
be used for mass programming. Activating the JTAG
interface and loading the test access port (TAP) with the
system programming instruction invokes the bootstrap
loader. Setting the SPE bit to one during reset through
the JTAG interface executes the bootstrap-loader mode
program that resides in the utility ROM. When program-
ming is complete, the bootstrap loader can clear the SPE
bit and reset the device, allowing the device to bypass
the utility ROM and begin execution of the application
software.
In addition, the ROM loader also enforces the memory-
protection policies. Passwords that are 16 words are
required to access the ROM loader interface.
______________________________________________________________________________________
Loading Flash Memory
DD
through a pullup resistor to
Infrared Module and Optional USB
ROM Loader
16-Bit Microcontrollers with
From user-application code, flash memory can be pro-
grammed using the ROM utility functions from either C
or assembly language. The function declarations below
show examples of some of the ROM utility functions
provided for in-application flash memory programming:
/* Write one 16-bit word to code address ‘dest’.
* Dest must be aligned to 16 bits.
* Returns 0 = failure, 1 = OK.
*/
int flash_write (uint16_t dest, uint16_t data);
To erase, the following function would be used:
/* Erase the given Flash page
* addr: Flash offset (anywhere within page)
*/
int flash_erasepage(uint16_t addr);
The in-application flash memory programming must call
ROM utility functions to erase and program any of the
flash memory. Memory protection is enforced by the
ROM utility functions.
Embedded debug hardware and software are devel-
oped and integrated to provide full in-circuit debugging
capability in a user-application environment. These hard-
ware and software features include the following:
• Debug engine
• Set of registers providing the ability to set breakpoints
Collectively, these hardware and software features sup-
port two modes of in-circuit debug functionality:
• Background mode:
• Debug mode:
The interface to the debug engine is the TAP control-
ler. The interface allows for communication with a bus
In-Application Flash Programming
on register, code, or data using debug service rou-
tines stored in ROM
CPU is executing the normal user program
Allows the host to configure and set up the in-circuit
debugger
Debugger takes over the control of the CPU
Read/write accesses to internal registers and memory
Single-step of the CPU for trace operation
In-Circuit Debug and JTAG
Interface
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