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December 14, 2001

79RC64574™ 79RC64575™

Pin Description Table

The following is a list of system interface pins available on the RC64574/575. Pin names ending with an asterisk (*) are active when low.

Pin Name

Type

Description

System Interface

ExtRqst*

I

External request

An external agent asserts ExtRqst* to request use of the System interface. The processor grants the request

by asserting Release*.

Release*

O

Release interface

In response to the assertion of ExtRqst* or a CPU read request, the processor asserts Release* and signals

to the requesting device that the system interface is available.

RdRdy*

I

Read Ready

The external agent asserts RdRdy* to indicate that it can accept a processor read request.

WrRdy*

I

Write Ready

An external agent asserts WrRdy* when it can now accept a processor write request.

ValidIn*

I

Valid Input

Signals that an external agent is now driving a valid address or data on the SysAD bus and a valid command

or data identifier on the SysCmd bus.

ValidOut*

O

Valid Output

Signals that the processor is now driving a valid address or data on the SysAD bus and a valid command or

data identifier on the SysCmd bus.

SysAD(63:0)

I/O

System address/data bus

A 64-bit address and data bus for communication between the processor and an external agent. In 64 bit

interface mode, during address phases only, SysAd(35:0) contains invalid address information. The remain-

ing SysAD(63:36) pins are not used. The whole 64-bit SysAD(63:0) may be used during the data transfer

phase. For all double-word accesses (read or write), the low-order 3 bits (SysAD[2:0]) will always be output as

zero during the address phase.

In 32-bit interface mode and in the RC64574, SysAD(63:32) is not used, regardless of Endianness. A 32-bit

address and data communication between processor and external agent is performed via SysAD(31:0).

SysADC(7:0)

I/O

System address/data check bus

An 8-bit bus containing parity check bits for the SysAD bus during data bus cycles.

In 32-bit mode and in the RC64574, SysADC(7:4) is not used. The SysADC(3:0) contains check bits for

SysAD(31:0).

SysCmd(8:0)

I/O

System command/data identifier bus

A 9-bit bus for command and data identifier transmission between the processor and an external agent.

SysCmdP

I/O

System Command Parity

A single, even-parity bit for the Syscmd bus. This signal is always driven low.

Clock/Control Interface

SysClock

I

SystemClock

The system clock input establishes the processor and bus operating frequency. It is multiplied internally by

2,3,4,5,6,7, or 8 to generate the pipeline clock (PClock).

Quiet VCC for PLL

Table 5 Pin Descriptions (Page 1 of 2)