TPCE260 User Manual Issue 1.0.3
Page 12 of 17
5.2.2 Voltage Keying Configuration
To prevent a PMC module from being plugged into a PMC system with a different PCI signaling voltage, the
PMC specification defines a voltage keying system with keying pins (on the PMC carrier board) and keying
holes (on the PMC module).
PMC modules supporting only 5V PCI signaling voltage provide a single keying hole for the 5V keying pin.
PMC modules supporting only 3.3V PCI signaling voltage provide a single keying hole for the 3.3V keying pin.
Universal PMC modules supporting both 3.3V and 5V PCI signaling voltages provide keying holes for both
voltage keying pins.
In certain system configurations it may be necessary to remove the keying pin from one location and assemble
it at the other keying pin location.
3.3V
Keying Pin
5V
Keying Pin
Figure 5-2 : PMC Voltage Keying
Use the following table to identify the required TPCE260 voltage keying for the actual PMC modules that are
to be used.
PMC
PCI Signaling
Voltage Capability
TPCE260 V_I/O
Configuration
TPCE260 5V
Keying Pin
TPCE260 3.3V
Keying Pin
3.3V only
3.3V
Not Installed
Installed
3.3V or 5V
3.3V
Not Installed
Installed
5V
Installed
Not Installed
5V only
5V
Installed
Not Installed
Table 5-4 : PCI Signal Voltage Configuration Matrix
