ARM9TDMI Signal Descriptions
A-10
Copyright © 1998, 1999 ARM Limited. All rights reserved.
ARM DDI0145B
A.6
Miscellaneous signals
Table A-6 Miscellaneous signals
Name
Direction
Description
BIGEND
Input
Big-Endian Configuration.
When this input is HIGH, the ARM9TDMI processor treats bytes in memory as being in
big-endian format. When it is LOW, memory is treated as little-endian.
ECLK
Output
External Clock.
The clock by which the ARM9TDMI is currently being clocked. This clock will reflect any
wait states applied by
nWAIT
, and once debug state has been entered by the debug clock.
nFIQ
Input
Not Fast Interrupt request.
This input causes the core to be interrupted if taken LOW, and if the appropriate enable in the
processor is active. The signal is level-sensitive and must be held LOW until a suitable
response is received from the processor. The
nFIQ
signal may be synchronous or
asynchronous, depending on the state of
ISYNC
.
GCLK
Input
Clock.
This clock times all ARM9TDMI memory accesses (both data and instruction), and internal
operations. The clock has two distinct phases—
phase 1
in which
GCLK
is LOW and
phase 2
in which
GCLK
is HIGH. The clock may be stretched indefinitely in either phase to allow
access to slow peripherals or memory. Alternatively,
nWAIT
may be used with a free running
GCLK
to stretch phase 2.
HIVECS
Input
High Vectors Configuration.
When LOW, the ARM9TDMI exception vectors start at address 0x00000000 (hexadecimal).
When HIGH, the ARM9TDMI exception vectors start at address 0xFFFF0000.
nIRQ
Input
Not Interrupt Request.
As
nFIQ
, but with lower priority. May be taken LOW to interrupt the processor when the
appropriate enable is active. The
nIRQ
signal
may be synchronous or asynchronous,
depending on the state of
ISYNC
.
ISYNC
Input
Synchronous Interrupts.
When LOW, this input indicates that the
nIRQ
and
nFIQ
inputs are to be synchronized by the
processor. When HIGH it disables this synchronization for inputs that are already
synchronous.
Содержание ARM9TDMI
Страница 1: ...Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ARM9TDMI Technical Reference Manual ...
Страница 6: ...Contents vi Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 12: ...Preface xii Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 16: ...Introduction 1 4 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 22: ...Programmer s Model 2 6 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 36: ...ARM9TDMI Processor Core Memory Interface 3 14 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 54: ...ARM9TDMI Coprocessor Interface 4 18 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 110: ...Test Issues 6 6 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 138: ...ARM9TDMI AC Characteristics 8 20 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 150: ...ARM9TDMI Signal Descriptions A 12 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 154: ...Index Index 4 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...