Chapter 8: PCI/G-Bus Bridge
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
8-10
Figure 8-6 PCI Master Writing to the G-Bus
8.2.4 PCI Master Reading from G-Bus Slave (Bridge Target Read)
The core implements a delayed read strategy as described below. The PGB will retry the G-
Bus Master if a G-Bus Master and a PCI Master initiate reads simultaneously.
8.2.4.1
Memory Read and I/O Read
A Master on the PCI Bus initiates a read to the PGB. If the data are not returned within 16
clock cycles, the core issues a Delayed Read to the PCI Master but continues fetching the
data from the G-Bus side of the core. For both burst and single Memory space transactions,
the PGB performs G-Bus pre-fetching until the PCI core indicates “last-word” fetched. When
the PCI core indicates “last-word”, the FIFO is flushed. The PGB uses a burst size of four
64-bit words for the speculative reads.
PCI
G-Bus
Parity
Fatal
Retry Logic
G-Bus
Handshake
Logic
Address
Generation
and Data
Folding to
32 bits for
32 bit
Slaves
Wait State
Logic
P
C
I
C
O
R
E
Status Reg.
Fatal Error
Interrupt
Logic
Parity Error
Interrupt
Logic
Word Count
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 ...