Integrating the ETB11
B-4
Copyright © 2002, 2003 ARM Limited. All rights reserved.
ARM DDI 0275D
B.3
Connecting the ETB11 in a 64-bit AHB system
The ETB11 AHB interfaces are 32-bits wide, and cannot therefore be directly
connected to a 64-bit AHB bus, such as that used in the ARM10 processor systems. A
simple bridge can be constructed that replicates the data on both halves of the bus, as
described in the
AMBA Specification
. The Verilog code shown in Example B-1
demonstrates how this can be done:
Example B-1 Connecting the ETB11 in a 64-bit system
<code>
// Logic to multiplex the 64-bit AHB bus to a 32-bit bus for 32-bit devices
always @(posedge HCLK)
begin
if(!HRESETn)
HWDATAMEMSelect <= 1'b0;
else if(HREADY)
HWDATAbusSelect <= HADDR[2];
end
assign HWDATAMEM32 = HWDATAMEMSelect ? HWDATAMEM[63:32] : HWDATAMEM[31:0];
// Recreate the 64-bit bus from the 32-bit Trace Buffer HRDATA bus
assign HRDATAMEM = {HRDATAMEM32,HRDATAMEM32};
</code>
If the code shown in Example B-1 is used then load/store multiple instructions that
access the ETB11 have unpredictable results because these use both halves of the 64-bit
bus at the same time. These accesses do not cause an AHB ERROR response, which
normally cause a Data Abort, so the error is not seen by the system. To remain
compatible with these systems, load/store multiple instructions are not permitted when
accessing the ETB11 to retrieve trace information (see
Restrictions on use of the AHB
This scheme can be used only when the trace RAM is to be used exclusively for tracing.
If the trace RAM is to be used as system memory then a full downsizer must be used
that bridges between 64-bit and 32-bit AHB buses, and convert a single 64-bit transfer
into two 32-bit transfers. This is provided as part of the
AMBA Design Kit
(ADK).
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 ...