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TI486 Microprocessor - Al Kossow's Bitsavers

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Register Set<br />

Figure 2-16. <strong>TI486</strong>DLCIE Debug Registers<br />

332222222222111111111<br />

1098765432109876543209876543210<br />

G G L G L G L G L G L<br />

000<br />

3 3 2 2 1 1 o 0 D E E 3 3 2 2 1 1 0 0 DR7<br />

LEN RIW LEN RIW LEN RIW LEN I R/W o 0<br />

o 0 o 0 o 0 o 0 o 0 o 0 o 0 o 0<br />

B B<br />

1 01 1 1 1 1 1 1 1 B B B B<br />

T S 3 2 1 0 DR6<br />

BREAKPOINT 3 LINEAR ADDRESS<br />

DR3<br />

BREAKPOINT 2 LINEAR ADDRESS<br />

DR2<br />

BREAKPOINT 1 LINEAR ADDRESS<br />

DR1<br />

BREAKPOINT 0 LINEAR ADDRESS<br />

DRO<br />

<strong>Al</strong>l bits marked as 0 or 1 are reserved and should not be modified.<br />

Table 2-13. DR6 and DR7 Field Definitions<br />

REGISTER<br />

DR6<br />

DR7<br />

FIELD<br />

Bi<br />

BT<br />

BS<br />

RlWi<br />

LENi<br />

Gi<br />

Li<br />

GD<br />

NUMBER<br />

OF BITS<br />

DESCRIPTION<br />

1 Bi is set by the processor if the conditions described by DRi, RlWi, and LENi<br />

occurred when the debug exception occurred, even if the breakpoint is not enabled<br />

via the Gi or Li bits.<br />

1 BT is set by the processor before entering the debug handler if a task switch has<br />

occurred to a task with the T bit in the TSS set.<br />

1 BS is set by the processor if the debug exception was triggered by the Single-step<br />

execution mode (TF flag in EFLAG$ set).<br />

2 Applies to the DRi breakpoint address register:<br />

00 - Break on instruction execution only<br />

01 - Break on data writes only<br />

10 - Not used<br />

11 - Break on data reads or writes<br />

2 Applies to the DRi breakpoint address register:<br />

00 - One byte length<br />

01 - Two byte length<br />

10 - Not used<br />

11 - Four byte length<br />

1 If set to a 1, breakpoint in DRi is globally enabled for all tasks and is not cleared by<br />

the processor as the result of a task switch.<br />

1 If set to a 1, breakpoint in DRi is locally enabled for the current task and is cleared<br />

by the processor as the result of a task switch.<br />

1 Global disable of debug register access. GD bit is cleared whenever a debug<br />

exception occurs.<br />

The debug address registers DRO-DR3 each contain the linear address for<br />

one of four possible breakpoints. Each breakpoint is further specified by bits<br />

in the debug control register (DR7). For each breakpoint address in DRO-DR3,<br />

there are corresponding fields L, RIW, and LEN in DR7 that specify the type<br />

of memory access associated with the breakpoint.<br />

2-32<br />

Programming Interface

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