GR740-UM-DS, Nov 2017, Version 1.7 437 www.cobham.com/gaisler
GR740
38 AMBA AHB/APB bridge with plug&play support
38.1 Overview
The AMBA AHB/APB bridge is a APB bus master according the AMBA 2.0 standard. The system
contains three AHB/APB bridges. Two on the Slave I/O AHB bus and one on the Debug AHB bus.
Figure 53. AHB/APB bridge block diagram
38.2 Operation
38.2.1 Decoding
Decoding (generation of PSEL) of APB slaves is done using the plug&play method explained in the
GRLIB IP Library User’s Manual. A slave can occupy any binary aligned address space with a size of
256 bytes - 1 MiB. Writes to unassigned areas will be ignored, while reads from unassigned areas will
return an arbitrary value. AHB error responses will never be generated.
38.2.2 Plug&play information
The plug&play information is mapped on a read-only address area at the top 4 KiB of each bridge’s
address space. Each plug&play block occupies 8 bytes. The address of the plug&play information for
a certain unit is defined by its bus index. If the bridge is mapped on AHB address 0xF0000000, the
address for the plug&play records is thus 0xF00FF000 + n*8.
Figure 54. APB plug&play information
APB SLAVE
APB SLAVE
AHB Slave
AHB/APB Bridge
Interface
•••
AHB BUS
APBI
APBO[0]
APBO[n]
AHBSI
AHBSO[n]
VENDOR ID DEVICE ID VERSION IRQ
31 24 23 12 11
45
0
ADDR C/P MASK TYPE
31 20 19 16 15
43
0
BAR
Configuration word
APB Plug&play record
0x00
0x04
10 9
00
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