AT89LP428 datasheet(114/149 Pages) ATMEL

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114

3654A–MICRO–8/09

AT89LP428/828

Figure 22-1. AT89LP428/828 On-chip Debug Connections

22.2

Software Breakpoints

The AT89LP428/828 microcontroller includes a BREAK instruction for implementing program

memory breakpoints in software. A software breakpoint can be inserted manually by placing the

BREAK instruction in the program code. Some emulator systems may allow for automatic inser-

tion/deletion of software breakpoints. The Flash memory must be re-programmed each time a

software breakpoint is changed. Frequent insertions/deletions of software breakpoints will

reduce the endurance of the nonvolatile memory. Devices used for debugging purposes should

not be shipped to end customers. The BREAK instruction is treated as a two-cycle NOP when

OCD is disabled.

22.3

Limitations of On-chip Debug

The AT89LP428/828 is a fully-featured microcontroller that multiplexes several functions on its

limited I/O pins. Some device functionality must be sacrificed to provide resources for On-chip

Debugging. The On-chip Debug System has the following limitations:

•The Debug Clock pin (DCL) is physically located on that same pin as Port Pin P3.6 and the

External Reset (RST). Therefore, neither P3.6 nor an external reset source may be emulated

when OCD is enabled.

• When using the Internal RC Oscillator during debug, DDA is located on the XTAL1/P4.0 pin.

The P4.0 I/O function cannot be emulated in this mode.

• When using the External Clock during debug, DDA is located on the XTAL2/P4.1 pin and the

system clock drives XTAL1/P4.0. The P4.1 I/O and CLKOUT functions cannot be emulated in

this mode.

• When using the Crystal Oscillator during debug, DDA is located on the P3.7 pin and the

crystal connects to XTAL1/P4.0 and XTAL2/P4.1. The P3.6 I/O function cannot be emulated

in this mode.

CLK = Internal RC

VCC

XTAL1

P3.6/RST

GND

DCL

DDA

CLK = External Clock

VCC

XTAL2

P3.6/RST

GND

DCL

DDA

XTAL1

CLK

CLK = Crystal Oscillator

VCC

P3.7

P3.6/RST

GND

DCL

DDA

XTAL1

XTAL2

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