Address Generation - ARM ETB11 Technical Reference Manual

Functional Description

2.6

Address generation

2.6.1

Write address generation

2.6.2

Read address generation

2-10

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.

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

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.

When trace capture and software access to registers are disabled, the RAM Read Pointer

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.

ARM DDI 0275D

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