MAXQ622G-0000 MAXIM [Maxim Integrated Products], MAXQ622G-0000 Datasheet - Page 28

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

16-Bit Microcontrollers with
Infrared Module and Optional USB
Figure 4. In-Circuit Debugger
master that can either be automatic test equipment or a
component that interfaces to a higher level test bus as
part of a complete system. The communication operates
across a 4-wire serial interface from a dedicated TAP
that is compatible with the JTAG IEEE Standard 1149.
The TAP provides an independent serial channel to com-
municate synchronously with the host system.
To prevent unauthorized access of the protected memo-
ry regions through the JTAG interface, the debug engine
prevents modification of the privilege registers and
disallows all access to system memory, unless memory
protection is disabled. In addition, all services (such as
register display or modification) are denied when code
is executing inside the system area.
For maximum flexibility the microcontroller can be pow-
ered by either the USB (V
connection is made to a valid V
internal voltage regulator generates a 3.3V supply volt-
age. When the internal voltage is at an adequate level, it
automatically powers itself from the USB supply. This is
especially beneficial in systems where the V
from a battery. In either case, the chip is fully functional
when operating from either the battery or the V
The power monitor is attached to the switched supply,
V
V
28
DDIO
DD
TMS
TDO
TCK
TDI
. This can be expressed as follows:
_____________________________________________________________________________________
. This supply is equivalent to the higher of V
If (V
CONTROLLER
MAXQ612
MAXQ622
TAP
DDB
> 3.0V or V
Power-Supply Selection
BUS
Operating Modes
(UTILITY ROM)
ROUTINES
BREAKPOINT
SERVICE
ENGINE
DEBUG
DEBUG
) or V
DDB
CONTROL
ADDRESS
BUS
DATA
> V
DD
power source, an
DD
. When a USB
)
DD
BUS
supply is
CPU
DDB
.
or
This means that if there is a power-fail event on V
the device is not powered from V
fail interrupt (PFI) if enabled. If the device is powered by
V
event is triggered. If the device is powered by V
and there is no supply on V
attempts to switch to V
and a PFI occurs. Some specific examples are given
below:
• Case 1: The device is powered from V
• Case 2: The device is set to be powered from V
• Case 3: The device is set to be powered from either
The lowest power mode of operation is stop mode. In this
mode, CPU state and memories are preserved, but the
CPU is not actively running. Wake-up sources include
external I/O interrupts, the power-fail warning interrupt,
wake-up timer, or a power-fail reset. Any time the micro-
controller is in a state where code does not need to be
executed, the user software can put the microcontroller
into stop mode. The nanopower ring oscillator is an inter-
nal ultra-low-power (400nA) 8kHz ring oscillator that can
be used to drive a wake-up timer that exits stop mode.
The wake-up timer is programmable by software in steps
of 125Fs up to approximately 8s.
The power-fail monitor is always on during normal opera-
tion. However, it can be selectively disabled during stop
BUS
the batteries are removed. Power decays until the
power-fail-reset trip point is hit, then the part goes into
low-power mode.
only, it is connected to USB, and the batteries are
removed. Response is identical to Case 1.
V
teries are removed. Because the part is already
powered from V
port is subsequently disconnected, power switches
over to V
trip point, and the part goes into low-power mode. As
long as there is sufficient charge on the V
capacitor, it supports the part in power-fail. The hold-
up time is similar to the MAXQ610 since the USB
port is powered only by V
powered from V
for a long time (V
nection, the power collapses to ground in less than a
second.
DD
and there is a supply on V
or V
DD
BUS
, the supply decays to the power-fail-reset
, it is connected to USB, and the bat-
then (V
else (V
BUS
BUS
DD
= 0), then upon USB port discon-
and no battery has been present
, nothing changes. If the USB
DD
DDIO
DDIO
, detects a power-fail event,
DD
BUS
= V
= V
and V
. Note that if the part is
BUS
DD
DDB
DD
, then no power-fail
, it causes a power-
)
)
BUS
fails, the chip
Stop Mode
DD
DD
DD
bypass
BUS
and
and
DD