Chapter 7 External Bus Controller
7-54
7.6
Flash ROM, SRAM Usage Example
Figure 7.6.1 illustrates example Flash ROM connections, and Figure 7.6.2 illustrates example SRAM
connections. Also, Figure 7.6.3 illustrates example connections with the SDRAM and the bus separated.
Since connecting multiple memory devices such as SDRAM and ROM onto a single bus increases the
load, 100 MHz class high-speed SDRAM access may not be performed normally. As a corrective measure,
there is a way of reducing the bus load by connecting a device other than SDRAM via a buffer. If such a
method is employed, directional control becomes necessary since the data becomes bidirectional.
The TX4937 prepares the BUSSPRT* signal for performing data directional control (see Figure 7.6.3).
BUSSPRT* is asserted when the External Bus Controller channel is active and a Read operation is being
performed.
Figure 7.6.1 Flash ROM (x16 Bits) Connection Example (32-bit Data Bus)
Figure 7.6.2 SRAM (x16 Bits) Connection Example (32-bit Data Bus)
ADDR[19:0]
ACE
*
CE
*
[0]
SWE
*
OE
*
DATA[31:0]
TX4937
ADDR[19:0]
A[19:0]
A20
CE
*
WE
*
OE
*
D[15:0]
ADDR[12]
(ADDR[20])
A[19:0]
A20
CE
*
WE
*
OE
*
D[15:0]
Flash ROM (x16 bits)
D[31:16]
D[15:0]
D[31:16]
BWE
*
[3:0]
ADDR[19:0]
CE
*
[1]
SWE
*
OE
*
DATA[31:0]
TX4937
ADDR[19:0]
UB LB
A[19:0]
CS
*
WE
*
OE
*
D[15:0]
SRAM (x16 Bits)
D[15:0]
UB LB
A[19:0]
CS
*
WE
*
OE
*
D[15:0]
BWE
*
[3]
BWE
*
[2]
BWE
*
[1]
BWE
*
[0]
Summary of Contents for TX49 TMPR4937
Page 1: ...64 Bit TX System RISC TX49 Family TMPR4937 Rev 2 0 ...
Page 4: ......
Page 13: ...Table of Contents ix TMPR4937 Revision History 1 ...
Page 14: ...Table of Contents x ...
Page 15: ...Handling Precautions ...
Page 16: ......
Page 18: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 40: ...3 General Safety Precautions and Usage Considerations 3 18 ...
Page 42: ...4 Precautions and Usage Considerations 4 2 ...
Page 43: ...TMPR4937 2005 3 Rev 2 0 ...
Page 44: ......
Page 52: ...Chapter 1 Overview and Features 1 6 ...
Page 156: ...Chapter 7 External Bus Controller 7 56 ...
Page 491: ...Chapter 16 Removed 16 1 16 Removed ...
Page 492: ...Chapter 16 Removed 16 2 ...
Page 493: ...Chapter 17 Removed 17 1 17 Removed ...
Page 494: ...Chapter 17 Removed 17 2 ...
Page 495: ...Chapter 18 Removed 18 1 18 Removed ...
Page 496: ...Chapter 18 Removed 18 2 ...
Page 497: ...Chapter 19 Removed 19 1 19 Removed ...
Page 498: ...Chapter 19 Removed 19 2 ...
Page 506: ...Chapter 20 Extended EJTAG Interface 20 8 ...
Page 530: ...Chapter 22 Pinout and Package Information 22 10 ...
Page 542: ...Chapter 24 Parts Number when Ordering 24 2 ...