21150-AB

Manufacturer Part Number21150-AB
DescriptionCommunications, Transparent PCI-to-PCI Bridge
ManufacturerIntel Corporation
21150-AB datasheet
 

Specifications of 21150-AB

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12.0
66-Mhz Operation
Some versions of the 21150 support 66 MHz operation. All 21150 versions marked 21150-Bx are
66MHz capable. Versions of the 21150 marked 21150-Ax are not capable of operation at 66 MHz.
Signal config66 must be tied high on the board to enable 66 MHz operation and to set the 66 MHz
Capable bit in the Status register and Secondary Status register in configuration space. If the 21150
version is not 66MHz capable, then config66 should be tied low. Signals p_m66ena and s_m66ena
should never be pulled high unless config66 is also high.
Signals p_m66ena and s_m66ena indicate whether the primary and secondary interfaces,
respectively, are operating at 66 MHz
secondary bus. Note that the PCI Local Bus Specification, Revision 2.1 restricts clock frequency
changes above 33 MHz to during PCI reset only.
The 66Mhz capable 21150 supports the following primary and secondary bus frequency
combinations:
66 MHz primary bus, 66 MHz secondary bus
66 MHz primary bus, 33 MHz secondary bus
33 MHz primary bus, 33 MHz secondary bus
The 21150 does not support 33 MHz primary/66 MHz secondary bus operation, where the
secondary bus is operating at twice the frequency of the primary bus. If config66 is high and
p_m66ena is low (66 MHz capable, primary bus at 33MHz), then the 21150 pulls down s_m66ena
to indicate that the secondary bus is operating at 33 MHz.
The 21150 generates the clock signals (s_clk_o<9:0>) for the secondary bus devices and its own
secondary interface. The 21150 divides the primary bus clock p_clk by two to generate the
secondary bus clock outputs whenever the primary bus is operating at 66 MHz and the secondary
bus is operating at 33 MHz. The bridge detects this condition when p_m66ena is high and
s_m66ena is low.
1.
In general, 66-MHz operation means operation ranging from 33 MHz up to 66 MHz.
Preliminary
Datasheet
1
. This information is needed to control the frequency of the
21150
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