Zilog Z16F2810 Manual de usuario descargar pdf (Pagina 69)

UM018809-0611 Software Traps

ZNEO

CPU Core

User Manual

Software Traps

The TRAP Vector instruction allows software to invoke any vectored service routine, par-

ticularly software-defined traps. The TRAP instruction executes the pointed service rou-

tine by the specified vector. Software traps use the same vector space as system exceptions

and interrupts. Like other vectors, the 32-bit trap vector value is stored in a memory quad.

Possible vectors are numbered from 0 to 255 (

0H to FFH). The possible vector space

includes memory quads

0000_0000H to 0000_03FCH. Each vector quad’s physical

address is 4

 Ve cto r.

Example. The following instruction executes a software-defined service routine pointed

to by Vector 255 stored in quad

0000_03FCH:

TRAP #FFH

A software trap service routine must execute an IRET instruction to return from the trap.

Other vectors not used by the CPU or peripherals are available for software-defined traps.

For example, Vector 255 (vector quad

0000_03FCH) is initialized with a pointer to a user-

input error handling routine, which is then invoked by a

TRAP FFH instruction.

For a list of vectors used by the CPU and internal peripherals, refer to the ZNEO product

specification that is specific to your device .

A TRAP instruction is used with exception or interrupt vectors but the TRAP instruction

does not sets any register bits in I/O memory that the corresponding service routine is

likely to inspect. For more information, see the Software Interrupt Generation

section on

page 46.

Some locations in the vector space may be reserved by the CPU for other uses. For exam-

ple, a typical ZNEO CPU uses the memory quad at

0000_0000H for option bits; there-

fore, Vector 00 is not available for service routines. Software can use the instruction

TRAP

#01

to invoke the RESET vector at 0000_0004H. For more information, see the TRAP

instruction on page 178.

Note:

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 215 216

Sin comentarios

Zilog Z16F2810 Manual de usuario Pagina 69