OCPRF100 MP Server System Technical Product Specification
Revision 1.0
10.2.10.5 ICMB Transmit ControlThe FPC’s TXD (transmitted) pin drives both the COM2’s SOUT_TTL_COM2 signal and the ICMB’s SOUT_TTL_ICMB signal. There is no interlock for preventing the FPC from simultaneously transmitting on both ICMB and COM2; in fact, this capability could be desirable.
The FPC drives the ICMB bus with the FPC’s TXD output whenever the ICMB_EN_LATCH is asserted (high).
10.2.10.6 COM2 Transmit ControlThe COM2 transmit signals are connected to either the FPC or the SMC Super I/O* (SIO) chip depending on the states of the COM2 signals. Note that this discussion is limited solely to the TXD signals since this is the only signal that the FPC can control.
The routing of COM2 to the SMC I/O chip or FPC and the routing of the ICMB to the FPC is controlled by two signals, COM2_TO_FP_EN_L and COM2_TO_SIO_EN. Note that if these two signals are not carefully controlled by firmware, the VCC_BACKUP can be shorted to ground. The VCC_BACKUP is shorted to ground via the SIO’s power pins. In this case, the power supplies will cycle the entire system and component damage may occur. When switching between enabling of these routings, it is important never to enable both these signals at the same time.
Table
Main Power | COM2_TO_FP_EN_L | COM2_TO_SIO_EN | Result |
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OFF | Deasserted (1) | Deasserted (0) | COM2 disconnected |
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| ICMB available† |
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|
|
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ON | Deasserted (1) | Deasserted (0) | COM2 disconnected |
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| ICMB available† |
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|
|
|
OFF | Asserted (0) | Deasserted (0) | COM2 routed to front panel |
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|
| ICMB available† |
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|
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ON | Asserted (0) | Deasserted (0) | COM2 routed to front panel |
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|
| ICMB available† |
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|
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ON | Deasserted (1) | Asserted (1) | COM2 connected with SMC* |
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| ICMB available† |
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|
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All Other States |
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| Possible main power cycle |
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| Possible component damage |
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|
|
|
†ICMB available means that if the ICMB_SOUT_EN signal is asserted then the FPC will transmit to the ICMB bus. The data that is transmitted comes from the microcontroller’s TXD output pin. Note that this capability is independent of the states of the COM2_TO_SIO_EN and COM2_TO_FPC_EN signals; it depends only on the state of the ICMB_SOUT_EN signal.
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