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  | Signal Description  | |
Table 3.  | PCI Interface Pins (Sheet 2 of 2) | ||
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Signal  | I/O  | Description  | |
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  | Parity Error: PERR# is driven by an external PCI device when it receives data that has a parity error.  | |
A_PERR#  | 
  | PERR# is driven by the 41210 in the following cases:  | |
I/O  | • when the 41210, as an initiator, detects a parity error during a read transaction  | ||
B_PERR#  | |||
  | • when the 41210, as a target, detects a parity error during a write transaction  | ||
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  | ||
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  | No external   | |
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A_SERR# | 
  | System Error: The 41210 samples SERR# as an input and conditionally forwards it to the PCI  | |
I  | Express*.  | ||
B_SERR#  | |||
  | No external   | ||
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  | ||
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A_REQ#[5:0]  | I  | PCI Requests: REQ# receives request inputs into the internal arbiter.  | |
B_REQ#[5:0]  | No external   | ||
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A_GNT#[5:0]  | 
  | PCI Grants: GNT# is the bus grant output corresponding to request input bits[5:0] from the internal  | |
O  | arbiter. GNT# indicates that an initiator can start a transaction on the PCI bus.  | ||
B_GNT#[5:0]  | |||
  | No external   | ||
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  | ||
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  | 66 MHz Enable: M66EN is an input signal from the PCI bus that indicates the speed of the PCI bus.  | |
A_M66EN | 
  | When it is high, the bus speed is 66 MHz. When it is low, the bus speed is 33 MHz. This signal is  | |
I/OD  | used to generate an appropriate clock (33 or 66 MHz) on the PCI bus.  | ||
B_M66EN | To tie high: Use an approximately 8.2 KΩ resistor to pull to VCC33.  | ||
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  | To tie low: Pull down to ground.  | |
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A_PCIXCAP | I  | ||
B_PCIXCAP | the 41210 can switch into   | ||
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  | PCI Lock: LOCK# indicates an exclusive bus operation and may require multiple transactions to  | |
A_LOCK#  | 
  | complete. This signal is an output from the bridge when it is initiating exclusive transactions on PCI.  | |
O  | LOCK# is ignored when PCI masters are granted the bus. Locked transaction do not propagate  | ||
B_LOCK#  | |||
  | upstream.  | ||
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  | ||
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  | No external   | |
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Total  | 118  | 
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Intel® 41210 Serial to Parallel PCI Bridge Developer’s Manual  | 17  |