Bcache Port

Table 4–45lists the combination of control pin assertion for RAM_TYPE B.

Table 4–45 Control Pin Assertion for RAM_TYPE B

TYPE_B

NOP

RA0

RA1

RA2

RA3

NOP

NOP

WA0

WA1

WA2

WA3

NOP

 

 

 

 

 

 

 

 

 

 

 

 

 

BcLoad_L

H

L

H

H

H

H

H

L

H

H

H

H

BcDataOE_L

H

L

L

L

L

H

H

L

L

L

L

H

BcDataWr_L

L

H

H

H

H

L

L

L

L

L

L

L

BcTagOE_L

H

L

H

H

H

H

H

L

H

H

H

H

BcTagWr_L

H

H

H

H

H

H

H

L

H

H

H

H

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 4–46lists the combination of control pin assertion for RAM_TYPE C.

Table 4–46 Control Pin Assertion for RAM_TYPE C

TYPE_C

NOP

RA0

RA1

RA2

RA3

NOP

NOP WA0 WA1 WA2 WA3 NOP

 

 

 

 

 

 

 

 

 

 

 

 

 

BcLoad_L

H

H

H

H

H

H

H

H

H

H

H

H

BcDataOE_L

H

H

L

L

L

L

L

H

H

H

H

H

BcDataWr_L

H

H

H

H

H

H

H

L

L

L

L

H

BcTagOE_L

H

L

L

H

H

H

H

H

H

H

H

H

BcTagWr_L

H

H

H

H

H

H

H

L

H

H

H

H

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 4–47lists the combination of control pin assertion for RAM_TYPE D.

Table 4–47 Control Pin Assertion for RAM_TYPE D

TYPE_D

NOP

RA0

RA1

RA2

RA3

NOP

NOP

WA0

WA1

WA2

WA3

NOP

 

 

 

 

 

 

 

 

 

 

 

 

 

BcLoad_L

H

L

H

H

H

H

H

L

H

H

H

H

BcDataOE_L

H

H

L

L

L

L

L

H

H

H

H

H

BcDataWr_L

H

H

H

H

H

H

H

L

L

L

L

H

BcTagOE_L

H

H

L

L

H

H

H

H

H

H

H

H

BcTagWr_L

H

H

H

H

H

H

H

L

H

H

H

H

 

 

 

 

 

 

 

 

 

 

 

 

 

Notes:

1.The NOP condition for RAM_TYPE B is consistent with bursting nonPentium style SSRAMs.

2.In both RAM_TYPE A and RAM_TYPE B, the pins BcDataOE_L and BcTagOE_L function changes from output-enable control to chip-select control.

3.In both RAM_TYPE C and RAM_TYPE D SSRAMs, the pins BcDataOE_L and BcTagOE_L function as an asynchronous output enable that envelopes the Bcache read data by providing an extra cycle of output enable.

Using these Cbox CSRs, late-write nonbursting and dual-data rate SSRAMs can be connected to the 21264/EV68A as described in Appendix E.

4–52Cache and External Interfaces

21264/EV68A Hardware Reference Manual

Page 140
Image 140
Compaq EV68A Control Pin Assertion for Ramtype B, Control Pin Assertion for Ramtype C, Control Pin Assertion for Ramtype D