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Functional Description
MEN Mikro Elektronik GmbH
58
20A014-00 E2 – 2007-08-16
2.16.7
VMEbus Master Interface
The A14C VMEbus master interface converts PCI bus cycles to VMEbus cycles.
The read/write cycles are performed in the A16, A24 and A32 address ranges of the
VMEbus. D08(E/O), D16 and D32 transfers will be executed. D64 transfers are
only possible with the DMA controller. The
MSTR – Master Control Register
(
0x0010
) (read/write)
enables the A14C to generate single RMW transfers or
Address-Only cycles.
MSTR – Master Control Register (
0x0010
) (read/write)
7..6
5
4
3
2
1
0
-
AONLY
POSTWR
IBERREN
BERR
REQ
RMW
AONLY
Enable single address only cycle
0 =
1 =
Normal cycle (default)
Adress only cycle
The master does not transfer data with this cycle. Other slaves can
detect this cycle to generate local interrupts.
Only 8-bit or 16-bit read cycles are allowed for address-only cycles!
This bit will be reset after the transmission was done.
POSTWR
Posted Write Access to VMEbus (not supported)
0 =
1 =
Delayed write access to VMEbus (default)
Posted write access to VMEbus
IBERREN
Interrupt Bus Error Enable
0 =
1 =
Local interrupt disabled if VMEbus bus error occurs (default)
Local interrupt enabled if VMEbus bus error occurs
BERR
Monitor for VMEbus
BERR#
signal
0 =
1 =
No VMEbus error (default)
VMEbus error occurred;
BERR#
signal asserted. Cleared by
writing 1.
REQ
Set VMEbus requester scheme
0 =
1 =
Request scheme for VMEbus master and interrupt handler is set to
Release On Request (ROR) (default)
Request scheme is set to Release When Done (RWD)
If this bit is changed from 0 to 1, i. e. from ROR to RWD, and there
were previous accesses over the master interface, it is recommended to
do a dummy read to free the bus.
RMW
Enable single Read-Modifiy-Write cycle
0 =
1 =
Normal cycle (default)
RMW cycle. Master keeps
AS#
asserted during back-to-back read/
write cycle.
This bit is automatically cleared after the RMW cycle and must be set
for the next RMW cycle again.
The following master/slave RMW accesses are allowed:
• Byte or word access in D16 mode
• Byte, word or long access in D32 mode
Note: During RMW cycles all interrupts on the host CPU should be masked.