Chapter 15: Serial Port Interface
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
15-5
This is compatible with the Atmel
*
AT25HP256/512. The bit rate is 2.08 MHz (fGBus = 66
MHz) or 1.56 MHz (fGBus = 50 MHz). = fGBus/4/SER.
(See Figure 15-1 above.)
BM/W locates the first byte on the LSB D[7:0], the second byte on D[15:8], third byte on
D[23:16], and the fourth byte on D[31:24], regardless of the CPU endianness. The same
ROM may be used in both the Big and Little Endian modes.
31
0
3
2
1
0
7
6
5
4
…
…
…
…
15.2.1 Boot ROM (64 KB)
The address range for 64 KB Boot ROM is from 0x1FC0_0000 to 0x1FC0_FFFF.
The acceptable data size of the Boot ROM area is as follows:
Word
(32-bit/4-Byte)
MIPS int. LW/SW
Double Word
(64-bit/8-Byte)
MIPS inst. LD/SD
Quad Word
(128-bit/16 Byte)
C790 Bus Width (instruction fetch)
4 QW
(512-bit/64-Byte)
C790 cache line size (cache refill)
8 QW
(1024-bit/128-Byte)
G-Bus maximum burst size
When a read transaction in this address range is on the G-Bus, BM/W initializes TSEI to the
Boot configuration (see Figure 15-2).
First, BM/W drives CE0 (SPI_Port0B) to Low, the BM/W issues a read command (0x03) to
serial ROM via TSEI. Then, 2 Bytes of the address is sent to Serial ROM. BM/W receives
the requested number of data bytes from Serial ROM via TSEI. Finally, BM/W drives CE0
(SPI_Port0B) to High. BM/W then returns the data on the G-Bus.
Important programming note: Do not attempt to access any TSEI registers while the boot
ROM area is accessed by both instruction fetch and data
read/write. BM/W initializes TSEI every time the boot ROM
area is accessed and this breaks any settings made by
software.
*
Atmel is a registered trademark of Atmel Corp.
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 ...