Figure 11 Interrupt Acknowledge Daisy Chain
The PME 68-1B has an on-board interrupt handler which can be configured to respond
to any group of request levels. Alternatively, the interrupt handler can be disabled and
the 68-1B used with an external interrupt handler.
VMEbus Arbitration
The VMEbus is designed to allow multi-master and multi-processor applications. Only
the current VMEbus master is able to carry out read or write transfers with other mod-
ules. This requires a special handshake scheme to define which module receives bus
mastership; this is the function of the VMEbus Arbiter.
The Arbiter is used to control the Data Transfer Bus (DTB). The DTB is the transport
medium for all data and includes the address, address modifier, strobe control and
acknowledge signals.
The Arbiter must reside in slot number 1 of the system because bus arbitration is daisy-
chained from slot 1 to 2 to 3 etc. Each system can have only one arbiter. This may be a
special card, another CPU card, or the one located on the PME68-1B.
Three arbiter types are defined in the VMEbus specification.
(1)
A four-level Bus Arbiter with a priority scheme
(2)
A four-level Bus Arbiter with a round-robin scheme
(3)
A one-level Bus Arbiter
The PME 68-1B provides a one-level Bus Arbiter only.
1
20
21
22
1
1
1
a
b
c
c
b
a
c
b
a
c
b
a
Slot 1
Slot 2
Slot 3
Slot n
20
21
22
20
21
22
20
21
22
NC
32
32
32
32
Pin 20
= IACK*
Pin 21
= IACKIN*
Pin 21
= IACKOUT*
PME68-1B Manual
Page 36 Issue 5
Summary of Contents for PME 68-1B
Page 8: ...Figure 1 The PME 68 1B Board Photograph not available in PDF PME 68 1B Manual Page 2 Issue 5...
Page 12: ...Figure 4 Component Layout Diagram P5 P4 P3 BAT PME 68 1B Manual Page 6 Issue 5...
Page 56: ...Figure 14 Link Areas BAT PME68 1B Manual Page 50 Issue 5...
