DMA
Controller
12-70
Figure 12–48. DMA Timing When Destination is an STRB, STRB0, STRB1, MSTRB Bus
Cycles
(H1)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Rate
Source
on chip
R1
R2
R3
R4
R5
Destination
STRB,
STRB0,
W1 W1 W1 W1 W2 W2 W2 W2 W3 W3 W3 W3 W4 W4 W4 W4
. . .
(1 + 2 +
Cw) T
STRB1,
MSTRB
bus
Cw
Cw
Cw
Cw
Source
STRB,
STRB0
R1
R1
R1
I
R2
R2
R2
I
{
STRB0,
STRB1
bus
Cr
Cr
(2 +
Cr + 2 + Cw) T + 0.5 (T – 1)
{
Destination
STRB,
W1 W1 W1 W1
W2 W2 W2 W2
. . .
STRB,
STRB0,
STRB1
bus
Cw
Cw
(3.5 +
Cr + 2 + Cw) T + .5 (T – 1)
{
(’C30 only)
Source
R1
R1
R1
R1
I
R2
R2
R2
R2
I
R3
R3
R3
R3
I
R4
R4
R4
R4
Source
IOSTRB
Cr
Cr
Cr
Cr
(3 + Cr + 2 + Cw) + (2 + Cw + max[1, Cr – Cw + 1])
(
T–1)
Destination
W1 W1 W1 W1
W2 W2 W2 W2
W3 W3 W3 W3
(
T–1)
STRB bus
Cw
Cw
Cw
Legend:
T
=
Number of transfers
W
=
Single-cycle writes
Cr
=
Source-read wait states
Rn
=
Multicycle reads
Cw = Destination-write wait states
Wn
=
Multicycle writes
R
=
Single-cycle reads
I
=
Internal register cycle
†
Write followed by read incurs in one extra half-cycle.