Chapter 7 External Bus Controller
7-7
7.3.5
Data Bus Size
The External Bus Controller supports devices with a data bus width of 8 bits, 16 bits, and 32 bits. The
data bus width is selected using the BSZ field of the Channel Control Register (EBCCRn). The address
bits output to each bit of the ADDR[19:0] signal change according to the mode. When access of a size
larger than the data bus width is performed, the dynamic bus sizing function is used to execute multiple
bus access cycles in order from the lower address.
7.3.5.1
32-bit Bus Width Mode
DATA[31:0] becomes valid.
Bits [21:2] of the physical address are output to ADDR[19:0]. The internal address bits [29:22],
which are the upper address, are multiplexed to external ADDR[19:12]. The maximum memory
size is 1 GB.
Table 7.3.4 Address Output Bit Correspondence in the 32-bit Mode
ADDR
Bit 19 18
17
16
15 14 13 12 11 10 9 8
7
6
5 4 3 2 1 0
Upper
Address 29
28
27
26
25
24
23
22
Lower
Address 21
20
19
18
17
16
15
14
13
12
11
10
9 8 7 6 5 4 3 2
When a Single cycle that accesses 1-Byte/1 half-word/1-word data is executed, 32-bit access is
executed only once on the external bus. 32-bit access is executed twice when performing 1-
double-word access. When a Burst cycle is executed, one 32-bit cycles are executed for each Burst
access when the Bus cycle tries to request a byte combination other than word data.
7.3.5.2
16-bit Bus Width Mode
DATA[15:0] becomes valid.
Bits [20:1] of the physical address are output to ADDR[19:0]. The internal address bits [28:21],
which are the upper address, are multiplexed to external ADDR[19:12]. In other words, the
address is shifted up one bit relative to the 32-bit bus mode when output. As a result, the
maximum memory size of the 16-bit bus mode is 512 MB.
Table 7.3.5 Address Output Bit Correspondence in the 16-bit Mode
ADDR
Bit 19 18
17
16
15 14 13 12 11 10 9 8
7
6
5 4 3 2 1 0
Upper
Address 28
27
26
25
24
23
22
21
Lower
Address 20
19
18
17
16
15
14
13
12
11
10
9 8 7 6 5 4 3 2 1
When a Single cycle that accesses 1-Byte or 1 half-word data is executed, 16-bit access is
executed only once on the external bus. 16-bit access is executed twice when performing 1-word
access. 16-bit access is executed four times when performing 1-double-word access. When a Burst
cycle is executed, two 16-bit cycles are executed for each Burst access when the Bus cycle tries to
request a byte combination other than word data.
Содержание TMPR4925
Страница 1: ...64 Bit TX System RISC TX49 Family TMPR4925 Rev 3 0 ...
Страница 4: ......
Страница 15: ...Handling Precautions ...
Страница 16: ......
Страница 18: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Страница 40: ...3 General Safety Precautions and Usage Considerations 3 18 ...
Страница 42: ...4 Precautions and Usage Considerations 4 2 ...
Страница 43: ...TMPR4925 ...
Страница 44: ......
Страница 54: ...Chapter 1 Features 1 8 ...
Страница 58: ...Chapter 2 Block Diagram 2 4 ...
Страница 88: ...Chapter 4 Address Mapping 4 12 ...
Страница 226: ...Chapter 8 DMA Controller 8 58 ...
Страница 260: ...Chapter 9 SDRAM Controller 9 34 ...
Страница 480: ...Chapter 15 Interrupt Controller 15 32 ...
Страница 554: ...Chapter 19 Real Time Clock RTC 19 8 ...
Страница 555: ...Chapter 20 Removed 20 1 20 Removed ...
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Страница 564: ...Chapter 21 Extended EJTAG Interface 21 8 ...
Страница 580: ...Chapter 22 Electrical Characteristics 22 16 ...
Страница 586: ...Chapter 23 Pin Layout Package 23 6 23 2 Package Package Type Package Code 256 pin PBGA PBGA 4L P BGA256 2727 1 27A4 ...
Страница 588: ...Chapter 24 Usage Notes 24 2 ...
Страница 590: ...Appendix A TX49 H2 Core Supplement A 2 ...