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3.7.1 PMC Rear I/O Tracking
The PMC site J14 pins 1 to 49 (or 1 to 64 in 'Peripheral Only' or 'Limited Host, Full
PMC User I/O' modes) are not mapped according to the conventional PMC Pn4 to
cPCI J2 scheme. The routing pattern used by the IMP2B is biased towards PMC cards
that use the Pn4 connector pins in pairs (1-3, 2-4, 5-7, 6-8, etc.) The signals are tracked
as 50 Ω single-ended to Ground and not as matched pairs (or triples). Sets of four
pairs (1 to 8, 9 to 16 ... 40 to 48 in Host mode, or 56 to 64 in 'Peripheral Only' and
'Limited Host, Full PMC User I/O' modes) are matched in length, but no two sets of
four pairs are the same length (e.g. 1 to 8 are all the same length, and 9 to 16 are all
the same length, but 1 to 8 are not the same length as 9 to 16). See the
description for the PMC user rear I/O pinout.
3.7.2 'Peripheral Only' Mode
The IMP2B supports a build of 'Peripheral Only' mode as a build option. In this
configuration, all 64 lines of PMC User I/O are routed to the cPCI
the ability of the IMP2B to operate as a cPCI Rack Host is sacrificed.
3.7.3 'Limited Host, Full PMC User I/O' Mode
The IMP2B supports a build of 'Limited Host, Full PMC User I/O' mode as a build
option. This allows the IMP2B to both operate as a Rack Host, supporting up to three
cPCI Slave cards, and provide access to all 64 PMC user I/O lines via the cPCI
J2
connector. This mode is primarily intended to be used in custom backplanes
designed specifically to support this configuration.
In this mode, the IMP2B uses the cPCI Geographical Address bits (3:0) to determine
whether it is to operate as a Rack Host, as the more usual SYSEN~ signal is re-
designated as a PMC User I/O signal.
The Spare link
enable Rack Host mode. With the link out, a Geographical Address of (3:0) = 0101
selects Host mode. With the link in, a Geographical Address of (3:0) = 0001
Host mode.
In a Host slot, an IMP2B supports up to three cPCI Slaves at 33 or 66 MHz, 3.3 V VIO
only.
22 IMP2B 3U cPCI Single Board Computer
CAUTION
Do not install an IMP2B built in 'Peripheral Only' mode into a Rack Host cPCI slot.
CAUTION
If an IMP2B built in this mode is to be used in the Host slot of a commercial rack, take extra care, as
some PMCs may have their I/O connected to backplane traces that they are not designed to drive (i.e.
GND or cPCI REQs, GNTs or CLKs).
(P5
5-6) determines the Geographical Address that is required to
NOTE
Geographical Address Bit (4) is unused.
J2 connector
J2
connector, but
b
selects
b
Publication No. IMP2B-0HH/5
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