Atari 130XE Uživatelský manuál stáhnout pdf (Strana 34)

3 Debugger and DOS

command displays the type of interrupt (IRQ or NMI) that caused activation of the

freezer, together with the original value of the corresponding interrupt vector. Additionally

the value of

VCOUNT

at the moment of the freezer activation as well as the calculated value

VCOUNT

at the moment the interrupt occurred are displayed. This command was mainly

introduced to test the freezer software and may be of little interest for most users. But

here’s a short description of the signiﬁcance and origin of the values.

When the freezer is activated, it maps the ROM with the freezer software into the

address space of the CPU and “reroutes” the high byte of the interrupt vector to the

ROM’s address, so the freezer software is started. Because the low byte is not changed,

there’s a full page of “NOP” instructions at the start of the freezer software. Therefore it

may be the case that the Atari has to execute through several “NOP” instructions to get

to the part that will read the value of VCOUNT.

Using the low-byte of the interrupt vector, the software tries to calculate the amount

of time it took to get through the “NOP” instructions and adjusts the

VCOUNT

value

accordingly. This way the program can be resumed at exactly the same position where

it was interrupted. This calculation is not 100% correct and may vary according to the

graphics mode. In the very rare case that the value is not correct and causes problems,

the command V<value can be used to set the VCOUNT value manually.

3.2.10 Activate direct I/O mode

Changes to hardware registers only become eﬀective after resuming, because in the

TURBO FREEZER

only the frozen system state is manipulated, as opposed to normal

debuggers which manipulate the real system sate. For experts the

TURBO FREEZER

oﬀers the possibility to activate the “direct I/O mode” and manipulate the real system

state also in the debugger.

DIO Display current mode: 0 = deactivated (default), 1 = activated

DIO<0 Deactivate direct I/O mode

DIO<1 Activate direct I/O mode

Caution:

When direct I/O mode is active, the freezer is “bypassed” and it becomes

likely to make mistakes. The freezer will not notice any changes to the hardware registers

in direct I/O mode. Therefore the same changes should also be performed again with direct

I/O mode switched oﬀ. Otherwise the freezer will overwrite the changes when resuming.

3.2.11 Display version number

The command

VER

prints the version number and the date of the freezer software in the

format 3.10 2012-11-09.

3.2.12 Display OS vectors

The

VEC

command displays the most important OS vectors of page 0 and 2 as an overview.

The output contains the symbolic name of each vector and its value.

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 63 64

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