
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
21-80
Freescale Semiconductor
External Memory Controller (EMC)
Figure 21-43. Effect of UPWAIT Signal
21.4.4.5
Synchronous Sampling of UPWAIT for Early Transfer Acknowledge
If UPWAIT is to be considered an asynchronous signal (which can be asserted/negated at any time), no
UPM RAM word must contain both WAEN = 1 and UTA = 1 simultaneously.
However, programming WAEN = 1 and UTA = 1 in the same RAM word allows UPM to treat UPWAIT
as a synchronous signal, which must meet set-up and hold times in relation to the rising edge of the bus
clock. In this case, as soon as UPM samples UPWAIT negated on the rising edge of the bus clock, it
immediately generates an internal transfer acknowledge, which allows a data transfer one bus clock cycle
later. The generation of transfer acknowledge is early because UPWAIT is not re-synchronized, and the
acknowledge occurs regardless of whether UPM was already frozen in WAIT cycles or not. This feature
allows the synchronous negation of UPWAIT to affect a data transfer.
LCSx
LGPL1
WAEN
Word n
Word n+1
c1
c2
c3
c4
c5
c6
c7
c8
UPWAIT
c9 c10 c11
c12
c13 c14
Word n+2
Wait
Wait
Word n+3
LCLK
T1
T2
T3
T4
A
B
C
D
TA