CHAPTER 8: DEBUGGER

Single-stepping(1)Types of single-stepping

There are two types of single-stepping available:

• Stepping through all instructions (STEP)

All instructions are executed one step at a time according to the PC, regardless of the type of instruction.

• Stepping through instructions except subroutines (NEXT)

The calr, calz and int instructions are executed under the assumption that one step constitutes the range of statements until control is returned to the next step by a return instruction. Other instructions are executed in the same way as in ordinary single-stepping.

In either case, the program starts executing from the current PC.

Table 8.8.4.2 Commands/menu items/tool bar buttons for single-stepping

Function

Command

Menu

Button

Stepping through all instructions

s

[Run Step]

 

 

 

 

 

Stepping through all instructions except subroutines

n

[Run Next]

 

 

 

 

 

When executing single-stepping by command input, the number of steps to be executed can be specified, up to 65,535 steps. When using menu commands or tool bar buttons, the program is executed one step at a time.

In the following cases, single-stepping is terminated before a specified number of steps is executed:

•When the [Key Break] button is clicked or the [Esc] key is pressed.

•When a map break or similar break occurs.

Single-stepping is not suspended by breaks set by the user such as a PC break or data break.

[Key Break] button ∗ When the program does not stop, use this button to forcibly stop it.

(2)Display during single-stepping

In the initial debugger settings, the display is updated as follows:

The display contents of the [Register] window are updated every step. If the [Register] window is closed, its contents are displayed in the [Command] window. This default display mode can be switched over by the md command so that the display contents are updated at only the last step in a specified number of steps.

The display of the [Source] and [Data] windows are updated after the specified number of step executions are completed.

(3)HALT and SLEEP states and interrupts

The CPU is placed in a standby mode when the halt or slp instruction is executed. An interrupt is required to cancel this mode.

The debugger has a mode to enable or disable an external interrupt for use in single-step operation.

Table 8.8.4.3 External interrupt modes

 

Enable mode

Disable mode

External interrupt

Interrupt is processed.

Interrupt is not processed.

halt and slp instructions

Executed as the halt instruction.

The halt and slp instructions are

 

Processing is continued by an

replaced with a nop instruction as

 

external interrupt or clicking on

the instruction is executed.

 

the [Key Break] button.

 

In the initial settings, the debugger is set to the interrupt disable mode. The interrupt enable mode can also be set by using the md command.

S5U1C63000A MANUAL

EPSON

147

(S1C63 FAMILY ASSEMBLER PACKAGE)