Specifications

Rev. 1.43
User's Guide
65
The A24 window
This window contains Flash, SRAM, and RTC zones.
This window occupies 1 MBytes and must be enabled with the VSBA24[WinA24On] bit before
use.
Its base address into the VME A24 space is defined with the VSBA24 register.
The Flash, SRAM, or RTC are accessed depending on the offset in this window as:
VME Offset Device Size Access
$0'0000-$7'ffff
SRAM memory 512 kBytes D8/D16/D32
$8'0000-$b'ffff
Flash memory 256 kBytes D16/D32
$c'0000-$c'7fff
RTC device 32 kBytes D8
Except for the RTC device, this window doesn’t include all memory map for Flash and SRAM memory.
The VSWA24 register is used to complete the high order local addresses for these two devices.
VSBA24
VME A24 space
VSBC-6862
RTC: 32kB
SRAM: 1MB
512kB
256kB
32kB
slave window
1MB
16MB
Flash bank: 8MB
VSWA24[FLAx]
VSWA24[SRAx]
Figure 20: VME slave window
The bootable Flash memory bank 0 is 8 MBytes, the VME slave window for Flash is 256 kBytes.
32 positions are needed to cover all Flash memory map. This is done using the VSWA24 register, bits
FLA18-FLA22. These bits are the respective high order addresses sent to the local Flash memory.
It’s to be noticed that the Flash memory is not accessible in D8 mode from VME. A D8 access will
always select 16 bits on the Flash memory.
When the J2[BootBank1] jumper is plugged-in, the VME bus can access the non-bootable Flash
memory bank, otherwise it can access the bootable Flash memory bank.
The SRAM memory is 1 MBytes, the VME slave window for SRAM is 512 kBytes.
2 positions are needed to cover this memory map. This is done using the VSWA24 register, bit
SRA19.
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