Chapter 8: PCI/G-Bus Bridge
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
8-14
reported to the PCI Master for PCI Master write operations. G-Bus errors are reported to the
PCI Master for PCI Master read operations by an abort. G-Bus errors will be reported on the
PCI Bus as a Target Abort regardless of whether this transaction has appeared on the G-
Bus or not.
8.2.10.2
Transactions with a G-Bus Master
During PCI transactions that have a G-Bus Master, the PCI bus may respond with a parity
error or a fatal error such as a Target Abort, or Non-response. When any of these PCI errors
occurs during a G-Bus Master write, the PGB posts an interrupt to the G-Bus, flushes any
pending requests, and preserves the G-Bus address of the failed transaction in a 1-deep
queue. The PGB makes this failed address available to the G-Bus interrupt handler. During
the interrupt pending period, errors subsequent to the first error are ignored.
When any of the above PCI errors occur during a G-Bus Master read, the PGB forces a retry
to the current cycle, issues a retry to all other cycles, and then causes a timeout for the next
request to the failed address.
An attempt by a G-Bus Master to cross a g2pWindow boundary is an error condition. The
PGB posts an interrupt to the G-Bus and the PGB goes through the G-Bus motion for the
transaction. The transaction is suppressed at the PGB and does not get to the PCI interface.
If this error occurs when the G-Bus Master is performing a read, undefined data are passed
to the G-Bus Master. The G-Bus address of the failed transaction is preserved in a 1-deep
queue and made available to the G-Bus interrupt handler.
Figure 8-10 Transactions with a G-Bus Master
PCI MASTER
PCI TARGET
GBUS MASTER
GBUS TARGET
Core
gbt
gbm
R (1)
W (2)
R (3)
W (1)
A
D
A
T
A
P
(1) Perr to PCI Master, transaction completed, No error reported to GBUS
(2) Perr from PCI target, transaction status is unknown, Error posted to GBUS Master, queue
Addr (PCI, GBUS) , Data, interrupt.
(3) Perr to PCI target, data in error, Addr (PCI, GBUS), interrupt.
Summary of Contents for TMPR7901
Page 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Page 14: ...Handling Precautions ...
Page 15: ......
Page 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 41: ...4 Precautions and Usage Considerations 4 2 ...
Page 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
Page 43: ......
Page 259: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 1 13 Removed ...
Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...