TMPR4955AF datasheet(130/168 Pages) TOSHIBA

130 / 168 page

Chapter 6 TX4955A System Interface

6-58

6.3.18

Signal Codes

System interface commands and data identifiers are encoded in five bits on the SysCmd

bus and transmitted between the processor and external agent during address and data

cycles.

•

When SysCmd (4)

SysCmd (4)

SysCmd (4) is a 0, the current cycle is an address cycle and SysCmd (3:0)

SysCmd (3:0)

contains a command.

•

When SysCmd (4)

SysCmd (4)

SysCmd (4) is a 1, the current cycle is a data cycle and SysCmd (3:0)

SysCmd (3:0)

identifies data.

For commands and data identifiers associated with external requests, all bits and fields

have a value or a suggested value.

For System interface commands and data identifiers associated with processor requests,

reserved bits and reserved fields in the command or data identifier are undefined, except

where noted.

For all System interface commands, the SysCmd bus specifies the system interface

request type. The encoding of SysCmd (4)

SysCmd (4)

SysCmd (4) for system interface commands is Table 6.3.3.

Table 6.3.3 Encoding of System Interface Commands in SysCmd (4)

SysCmd(4)

Command

Address Cycle

Data Cycle

For address requests, the remainder of the SysCmd bus specifies the attributes of the

address request, as follows:

•

SysCmd (3)

SysCmd (3) encodes the address request type.

•

SysCmd (2:0)

SysCmd (2:0) indicates the size of the address requests.

The encoding of SysCmd (3:2) for address requests is shown in Table 6.3.4.

Table 6.3.4 Encoding of SysCmd(3) and SysCmd(2) for Address Cycle

SysCmd (3)

Command

SysCmd (2) Request Size

Read Request

Single data

Write Request

Block data

Note:TX4955A support only External Single data write request.

The encoding of SysCmd (1:0)

SysCmd (1:0)

SysCmd (1:0) for block or single address requests is shown in Table 6.3.5

and 6.3.6, respectively.

Table 6.3.5 Encoding of SysCmd (1:0) for Block Address Requests

SysCmd (1:0)

Block Size

Reserved.

Four words(only Data cache).

Eight worde.

Reserved.

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