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 0xF0 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
4
5
0
ADDR
C/P
MASK
TYPE
31
20 19
16 15
4 3
0
BAR
Configuration word
APB Plug&play record
0x00
0x04
10 9
00