Motorola DSP96002 , 2 - 18 DSP96002 USERS MANUAL MOTOROLA, , Figure 2-9. Bus Handshake State Diagram

2 - 18 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 —B–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 & ^( ^—B–G & —B–B )
XY = ext_acc_req & ^( ^—B–G & —B–B )
XZ = ext_acc_req & ( ^—B–G & —B–B )
XW = ^ext_acc_req & ( ^—B–G & —B–B )
YX = ^ext_acc_req & ^( ^—B–G & —B–B ) (note 1)
YY = ext_acc_req & ^( ^—B–G & —B–B )
YZ = ext_acc_req & ( ^—B–G & —B–B )
YW = ^ext_acc_req & ( ^—B–G & —B–B ) (note 1)
ZX = ^ext_acc_req & —B–G
ZY = ext_acc_req & —D—B–G & end_of_sequence (note 3)
ACTIVE_
MASTER
(Z)
—B–R = 0
—B–A = 0
Figure 2-9. Bus Handshake State Diagram
REQUEST_BUS
(Y)
—B–R = 0
—B–A = 1
PARKING_
MASTER
(W)
—B–R = —
R–H
IDLE
(X)
—B–R = —R–
H
YY XX
ZZ WW
(delayed)
ZY YZ
ZX
XZ
WY
(non-existant)
YX (illegal)
XY
ZW
WZ
WX XW
(delayed )YW (illegal)