Actis VSBC-6872 Series, Руководство пользователя

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User's guide
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Note that an external VME access to one of these zones (VSBC-6872 slave access), doesn’t block the
host processor with the SDRAM, PMC module, or communication ports. For example, the MPC8270 can
access the SDRAM while an external VME master accesses the local SRAM memory. Moreover, an
external master can access the VSBC-6872 before it is initialized. All slave functions are independent of
the MPC8270 state.
These zones are divided in three windows: one A16 window and two A24 windows.
A16 window
This window gives access to a subset of the bridge registers.
This windows occupies 2kBytes.
Its base address is defined with 5 jumpers (J2). Please refer to
7.2 Board jumpers for jumper
configuration.
VME slave register memory map:
Offset Name Mode Description Access
0x01 VSMAIL RW VME Slave Mailbox D8/D16
0x03 VSBA24 RW VME Slave Base Window A24 D8/D16
0x05
VSWA24 RW VME Slave Window A24 management D8/D16
0x07 VIVEC RW VME Interrupter Vector D8/D16
0x09 SRESR WO Software Reset Register D8/D16
0x0b XSAV24 RW Extended SRAM Access from VME A24 D8/D16
0x0d
VIL RW VME Interrupter Interrupt Level D8/D16
Table 15 - Bridge registers accessible from VMEbus
For more flexibility, these registers are also accessible from the MPC8270.
A24 windows
Two A24 windows are defined.
One is specified by the VSBA24 register and gives access to the Flash, SRAM, and RTC devices. It
occupies 1 MByte and is enabled by setting VSBA24[WinA24On].
The Flash, SRAM or RTC are accessed depending on the offset in the VSBA24 window as:
VME Offset Device Size Access
0x0'0000-0x7'ffff SRAM memory 512 kBytes D8/D16/D32
0x8'0000-0xb'ffff
Flash memory 256 kBytes D16/D32
0xc'0000-0xc'7fff RTC device 32 kBytes D8
Table 16 - A24 Slave memory map
Except for the RTC device, this window does not include all memory map for Flash and SRAM memory.
The VSWA24 register is used to complete the high order local addresses for these devices (
Figure 11 ).
The 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 FLA23-FLA18.
These bits are the respective high order addresses sent to the local Flash memory. Note that the Flash
memory is not accessible in D8 mode from VME. A D8 access will always select 16 bits on the Flash
memory.
The SRAM memory is 1 MByte, 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.
The second window is specified by the XSAV24 register and gives access to the whole SRAM memory (1
MB or 2 MB option). It occupies 1 or 2 MBytes and is enabled by setting XSAV24[EN] (
Figure 12 ). The
advantage of this window over the one defined by VSBA24 is that the whole SRAM is visible in a single
VME window.
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