Chapter 9: DMA Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
9-7
9.1.9
32-/64-bit G-Bus I/O
The DMAC supports 32-/64-bit G-Bus I/O using dynamic bus sizing. When the DMAC
initiates a G-Bus cycle, the I/O device communicates its device size through gAck32B and
gAck64B.
For 32-bit devices, the DMAC reads or writes data on the lower 32 bits of the G-Bus only.
9.1.10 Memory Byte Alignment Support
If the C790 bus memory start address is not quad-word aligned, the DMAC divides the
memory access into C790 bus Single operations followed by C790 bus Burst operations. If
the C790 bus memory end address is also not quad-word aligned, the DMAC finishes with a
single C790 bus Single operation. Figure 9-5 is an example of the cycle division in little
endian memory. In this example, the memory transfer is divided into a Single cycle, a Burst
cycle of 2 quad-words, two burst cycles of 8 quad-words, and then two single cycles.
000000000 Hex
FFFFFFFF0 Hex
8-QW Boundary
8-QW Boundary
8-QW Boundary
1QW
Unaligned Address
Cycle Division
000000000 Hex
FFFFFFFF0 Hex
8-QW Boundary
8-QW Boundary
8-QW Boundary
1QW
Figure 9-5 C790 Bus Unaligned Address Cycle Break Down
The same occurs in the case of G-Bus memory access. If the G-Bus memory start address
is not quad-word aligned, the DMAC divides the memory access into G-Bus Single
operations followed by G-Bus Burst operations. If the G-Bus memory end address is also
not quad-word aligned, the DMAC finishes with a G-Bus Single operation.
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 ...