Memory Controller

When writes goes to a card sockets and a byte has been masked via an internal byte enable, the write does not occur on the external bus. For reads, one half-word is always read from the socket, even if only 1 byte is requested. In some cases, based on internal address alignment, one word is read, even if only 1 byte is requested.

All DMA modes are supported in the Card interface increment the address.

Table 6-31. Common Memory Space Write Commands

nPCE2

nPCE1

MA<0>

nPOE

nPWE

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

1

0

Odd Byte

Even Byte

 

 

 

 

 

 

 

1

0

0

1

0

Unimportant

Even Byte

 

 

 

 

 

 

 

1

0

1

1

0

Unimportant

Odd Byte

 

 

 

 

 

 

 

Table 6-32. Common Memory Space Read Commands

nPCE2

nPCE1

MA<0>

nPOE

nPWE

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

0

1

Odd Byte

Even Byte

 

 

 

 

 

 

 

Table 6-33. Attribute Memory Space Write Commands

nPCE2

nPCE1

MA<0>

nPOE

nPWE

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

1

0

Unimportant

Even Byte

 

 

 

 

 

 

 

1

0

0

1

0

Unimportant

Even Byte

 

 

 

 

 

 

 

1

0

1

1

0

Unimportant

Unimportant

 

 

 

 

 

 

 

Table 6-34. Attribute Memory Space Read Commands

nPCE2

nPCE1

MA<0>

nPOE

nPWE

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

0

1

Unimportant

Even Byte

 

 

 

 

 

 

 

Table 6-35. 16-Bit I/O Space Write Commands (nIOIS16 = 0)

nPCE2

nPCE1

MA<0>

nPIOR

nPIOW

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

1

0

Odd Byte

Even Byte

 

 

 

 

 

 

 

1

0

0

1

0

Unimportant

Even Byte

 

 

 

 

 

 

 

1

0

1

1

0

Unimportant

Odd Byte

 

 

 

 

 

 

 

Table 6-36. 16-Bit I/O Space Read Commands (nIOIS16 = 0)

nPCE2

nPCE1

MA<0>

nPIOR

nPIOW

MD[15:8]

MD[7:0]

 

 

 

 

 

 

 

0

0

0

0

1

Odd Byte

Even Byte

 

 

 

 

 

 

 

Intel® PXA255 Processor Developer’s Manual

6-65

Page 247
Image 247
Intel PXA255 Common Memory Space Write Commands, Common Memory Space Read Commands, Attribute Memory Space Write Commands