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SIS Documentation
SIS3820
VME Scaler
Page 16 of 79
6 VME
Addressing
As the SIS3820 features memory options with up 512 Mbytes of SDRAM, A32 addressing
was implemented as the only option. Hence the module occupies an address space of
0xFFFFFF Bytes (i.e. 16 MBytes).
The SIS3820 firmware addressing concept is a pragmatic approach to combine standard
rotary switch style settings with the use of VME64x backplane geographical addressing
functionality.
The base address is defined by the selected addressing mode, which is defined by jumper
array J1 and possibly SW4 and SW3 (in non geographical mode).
Function
EN_A32
reserved
EN_GEO
SDRAM_SIZE open: 64 MByes
J1
SDRAM_SIZE
closed: 512 MBytes
EN_A32
EN_GEO
Description
0
0
non A32 addressing, reserved for future use
0
1
non A32 addressing, reserved for future use
1
0
A32 addressing, address compared with SW3/SW4
1
1
A32 addressing, address compared with geographical address
0: jumper open, 1: jumper closed
The table below illustrates the possible base address settings.
J1 Setting
Bits
GEO
31 30 29 28 27 26 25 24
- SW4
SW3
x
y
y
y
GA4
GA3
GA2
GA1
GA0
Shorthand Explanation
SW3/SW4 Setting of rotary switch SW3 or SW4 respective
y don’t
care
GA0-GA4
Geographical address bit as defined by the VME64x(P) backplane
Notes:
•
This concept allows the use of the SIS3820 in standard VME as well as in VME64x
environments, i.e. the user does not have to use a VME64x backplane.
•
The factory default setting is 0x38000000 (i.e. SW4=3, SW3=8, EN_A32 closed and
EN_GEO open/disabled)