PM7375-SC datasheet(45/430 Pages) PMC

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PM7375 LASAR-155

DATA SHEET

PMC-931127

ISSUE 6

LOCAL ATM SAR & PHYSICAL LAYER

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

REQB

Output 201

The active low PCI bus request (REQB) signal is used

by the LASAR-155 to request an external arbiter for

control of the PCI bus. REQB is forced low when the

internal PCI DMA controller requires access to the

packet memory. Otherwise, REQB is forced high.

REQB is updated on the rising edge of PCICLK.

GNTB

Input

200

The active low PCI bus grant (GNTB) signal is used to

grant control of the PCI to the LASAR-155 in response

to a bus request via the REQB output. When GNTB is

high, the LASAR-155 does not control the PCI bus

and thus must wait. When GNTB is low, the external

arbiter has granted the LASAR-155 control of the PCI

bus. However, the LASAR-155 does not proceed until

the FRAMEB signal is high indicating no current

transactions.

GNTB is sampled using the rising edge of PCICLK.

PERRB

Output

The active low parity error (PERRB) signal indicates

when the LASAR-155 detects a parity error over the

AD[31:0] and C/BEB[3:0] signals when compared to

the PAR input. PERRB is high when no parity error is

detected. PERRB is forced low for the cycle

immediately following the offending PAR cycle.

PERRB is enabled using a bit in the Control register in

the PCI Configuration registers space. In addition,

regardless of whether output, PERRB is enabled or

not, parity errors are indicated in the Status register in

the PCI Configuration registers space.

PERRB is updated on the rising edge of PCICLK.

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