Functional Description
2-10
Copyright © 2002, 2003 ARM Limited. All rights reserved.
ARM DDI 0275D
2.6
Address generation
There are two RAM address pointer registers:
•
the RAM Write Pointer Register is selected during trace capture
•
the RAM Read Pointer Register is used as the RAM address source:
—
when trace capture is disabled
—
if software access to registers is disabled.
TraceCaptEn
selects which pointer is used.
2.6.1
Write address generation
The RAM Write Pointer Register sets the trace RAM start address. It must be
programmed before trace capture is enabled. The RAM Write Pointer Register
increments when the
DataValid
flag is asserted by the Data Formatter. Reading the
register returns the current RAM Write Pointer Register value. The RAM Write Pointer
Register can be read back at any time. However if the TAP controller clock,
DBGTCK,
is asynchronous to
CLK
, the value might be indeterminate if read while trace capture
is enabled. Therefore, the pointer must be accessed when
TraceCaptEn
is deasserted.
The RAM Write Pointer Register is not affected by AHB writes to the RAM.
2.6.2
Read address generation
When trace capture and software access to registers are disabled, the RAM Read Pointer
Register generates the RAM address. Updating the RAM Read Pointer Register
automatically triggers a RAM access to ensure the RAM data output is up-to-date.
Either writing to the RAM Read Pointer Register or reading the RAM Data Register
updates the RAM Read Pointer Register. The RAM Read Pointer Register increments
each time the RAM Data Register is read. The RAM Read Pointer Register can be
accessed at any time. Reading the RAM Read Pointer Register returns its current value,
the RAM read address. The RAM Read Pointer Register is not affected by AHB reads
from the RAM.
Summary of Contents for ETB11
Page 6: ...List of Tables vi Copyright 2002 2003 ARM Limited All rights reserved ARM DDI 0275D ...
Page 8: ...List of Figures viii Copyright 2002 2003 ARM Limited All rights reserved ARM DDI 0275D ...
Page 46: ...Functional Description 2 26 Copyright 2002 2003 ARM Limited All rights reserved ARM DDI 0275D ...
Page 70: ...Signal Descriptions A 6 Copyright 2002 2003 ARM Limited All rights reserved ARM DDI 0275D ...
Page 78: ...Glossary Glossary 4 Copyright 2002 2003 ARM Limited All rights reserved ARM DDI 0275D ...