Rainbow Electronics MAXQ3120 - Manual (Page 25)

In-Circuit Debug
Embedded debugging capability is available through
the JTAG-compatible TAP. Embedded debug hardware
and embedded ROM firmware provide in-circuit
debugging capability to the user application, eliminat-
ing the need for an expensive in-circuit emulator.
Figure 4 shows a block diagram of the in-circuit debug-
ger. The in-circuit debug features include:
• Hardware debug engine
• Set of registers able to set breakpoints on register,
code, or data accesses
• 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.
Serial Peripherals
The MAXQ3120 incorporates two 8051-style universal
synchronous/asynchronous receiver/transmitters. The
USARTs allow the device to conveniently communicate
with other RS-232 interface-enabled devices, as well as
PCs and serial modems when paired with an external
RS-232 line driver/receiver. The dual independent
USARTs can communicate simultaneously at different
baud rates with two separate peripherals. The USART
can detect framing errors and indicate the condition
through a user-accessible software bit.
The time base of the serial ports is derived from either a
division of the system clock or the dedicated baud
clock generator. The following table summarizes the
operating characteristics as well as the maximum baud
rate of each mode.
Serial port 0 contains additional functionality to support
low-speed infrared transmission in combination with the
PWM function of timer 2. When enabled in this mode,
the serial port automatically outputs a waveform gener-
ated by combining the normal serial port output wave-
form with the PWM carrier waveform output by timer 2,
using a logical OR or logical NOR function. The output
of serial port 0 in this mode can be used to drive an
infrared LED to communicate using a fixed-frequency
carrier modulated signal. Depending on the drive
strength required, the output may require a buffer when
used for this purpose.
MAXQ3120
High-Precision ADC
Mixed-Signal Microcontroller
____________________________________________________________________ 25
MODE TYPE START BITS DATA BITS STOP BIT MAX BAUD RATE AT 8MHz
Mode 0 Synchronous — 8 — 2Mbps
Mode 1 Asynchronous 1 8 1 250kbps
Mode 2 Asynchronous 1 8 + 1 1 250kbps
Mode 3 Asynchronous 1 8 + 1 1 250kbps
Figure 4. In-Circuit Debugger
TAP
CONTROLLER
CPU
DEBUG
ENGINE
DEBUG
SERVICE
ROUTINES
(UTILITY ROM)
TMS
TCK
TDI
TDO
CONTROL
BREAKPOINT
ADDRESS
DATA
MAXQ3120