TMPR4955AF datasheet(105/168 Pages) TOSHIBA

105 / 168 page

Chapter 6 TX4955A System Interface

6-33

6.3

System Interface of TX4300 type protocol mode

In TX4955A, it is built in system interface function corresponding to TX4300 type protocol. A

selection of above-mentioned R5000 type protocol mode or TX4300 type protocol mode increases

by external pin (MODE43* : 117 pin).

MODE43* = 0: TX4300 type protocol

MODE43* = 1: R5000 type protocol

Note:

In TX4300 type protocol mode of TX4955A, there is not PReq signal. Therefore there is the

need that PReq terminal of an external agent is always fixed in "L" Level. And there is not a

function too to show that protocol errors were detected.

But search of protocol errors is possible when I have a counter built-in in TX4955A inside,

and there is not lead reply between constant time because it is established the function that

an exception generates bus error.

6.3.1

System Interface Description of TX4300 Type Protocol Mode

The TX4955A processor has a 32-bit address/data interface. The System interface

consists of:

•

32-bit address and data bus, SysAD

SysAD

•

5-bit command bus, SysCmd

SysCmd

•

five handshake signals:

– EValid

EValid

EValid*, PValid

, PValid

, PValid*

– EReq

EReq

EReq*

– PMaster

PMaster

PMaster*, EOK

, EOK

, EOK*

Table 6.3.1 System Interface Signals

(TX4300 type protocol mode is MODE43* = 0)

Signal

I/O

Function

SysAD (31:0)

I/O

Address and data transfer bus, multiplexed between the processor and an external agent.

SysCmd (4:0)

I/O

Used for command and data identifier transmission between the processor and an external agent.

SysCmd (8:5) / GND

When TX4300 type protocol mode, those pin output “L”.

SysADC (3:0) / GND

When TX4300 type protocol mode, those pin output “L”.

SysCmdP / GND

When TX4300 type protocol mode, this pin output “L”.

ValidIn* / EValid*

During the cycle it is asserted, EValid* indicates an external agent is driving a valid address or valid

data on the SysAD bus, and a valid command or data identifier on the SysCmd bus.

ValidOut* / PValid*

During the cycle it is asserted, PValid*, indicates the processor is driving a Valid address or Valid

data on the SysAD bus, and a valid command or data indentifier on the SysCmd bus.

ExtRqst* / Ereq*

Indicates an external agent is requesting System interface bus ownership.

Release* / PMaster

Indicates an external agent is capable of the system interface bus.

WrRdy* / EOK*

Indicates an external agent is capable of accepting a processor request.

RdRdy* / GND

When TX4300 type protocol mode this pin output “L”.

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