Figure 2-9. bus handshake state diagram – Motorola DSP96002 User Manual

Page 21

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DSP96002 USER’S MANUAL

MOTOROLA

Likewise, when executing the read part of a RMW access, the end_of_sequence signal is deasserted.

This signal is used to give up bus ownership if

—

–

G is deasserted during bus transfers. The state ma-

chine which controls the bus handshake is illustrated in Figure 2.9.

The transition arcs are labeled by two letters which denote its source and destination states. The equa-

tions of the transition arcs are described as follows:

XX = ^ext_acc_req

& ^( ^

—

–

G &

—

–

B )

XY = ext_acc_req

& ^( ^

—

–

G &

—

–

B )

XZ = ext_acc_req

& ( ^

—

–

G &

—

–

B )

XW = ^ext_acc_req

& ( ^

—

–

G &

—

–

B )

YX = ^ext_acc_req

& ^( ^

—

–

G &

—

–

B )

(note 1)

YY = ext_acc_req

& ^( ^

—

–

G &

—

–

B )

YZ = ext_acc_req

& ( ^

—

–

G &

—

–

B )

YW = ^ext_acc_req

& ( ^

—

–

G &

—

–

B )

(note 1)

ZX = ^ext_acc_req

—

–

ZY = ext_acc_req

—

–

G & end_of_sequence

(note 3)

ACTIVE_

MASTER
(Z)

—

–

R = 0

—

–

A = 0

Figure 2-9. Bus Handshake State Diagram

REQUEST_BUS

(Y)

—

–

R = 0

—

–

A = 1

PARKING_

MASTER
(W)

—

–

R =

—

–

IDLE

(X)

—

–

R =

—

–

(delayed)

(non-existant)

YX (illegal)

(delayed

)

YW (illegal)