TNETX4080 Datasheet, PDF (47/64 Pages) Texas Instruments – ThunderSWITCH IIE 8-PORT 10-/100-MBIT/S ETHERNETE SWITCH

TNETX4080
ThunderSWITCH II^™ 8-PORT 10-/100-MBIT/S ETHERNET^™ SWITCH
SPWS050A – AUGUST 1998 – REVISED NOVEMBER 1998
system test capabilities
RDRAM
The external RDRAM can be read and written using regular DIO accesses following a stop. Individual bytes can
be read and written. However, as the RDRAM memory actually is accessed in 128-byte pages, performing
128-byte accesses is the most efficient.
To access the RDRAM, the TNETX4080 must not be operating. The user must perform a reset and not set start
in SysControl. Both start and initd in SysControl must be 0. In addition, rdinit in SysTest must be set, indicating
that the RDRAM has initialized. This initialization sequence occurs automatically after a hard reset.
Read or write accesses to RDRAM are invoked via rdram and rdwrite in SysTest. Setting rdram to 1 causes a
128-byte transfer between the device and the RDRAM memory to be initiated.
D The transfer direction is determined by rdwrite.
D The external memory byte address for the access is specified by ramaddress in RAMAddress.
D Data to be read from or written to RDRAM is accessed indirectly via RAMData.
writing RDRAM
Writing to RDRAM memory is accomplished as follows:
1. Write the byte address for the access to ramaddress in RAMAddress.
2. Write the data for the access to RAMData. Up to 64 bytes can be written, if all but the six least significant
bits of the address are the same for all the data. Inc in RAMAddress can be used to autoincrement the
address.
3. Set rdwrite = 0 and rdram = 1 (these can be written simultaneously).
4. If required, poll rdram until it becomes 0. This indicates that the write has completed.
reading RDRAM
Reading from RDRAM memory is accomplished as follows:
1. Write the byte address for the access to ramaddress in RAMAddress.
2. Set rdwrite = 1 and rdram = 1 (these can be written simultaneously).
3. Poll rdram until it becomes 0. This indicates that the read has completed.
4. Read the data for the access to RAMData. Up to 64 bytes can be read, provided that all but the six least
significant bits of the address are the same for all the data. Inc in RAMAddress can be used to autoincrement
the address.
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