MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 301

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

6.9 AC ELECTRICAL SPECIFICATIONS—DMA
MOTOROLA
NOTES:
1. DREQ is sampled on the falling edge of CLK in cycle steal and burst modes.
2. If #80 is satisfied for DREQ, #81 may be ignored.
3. BR will not be asserted while BG, HALT, or BERR is asserted.
4. Specifications are for DISABLE CPU mode only.
5. DREQ, DACK, and DONE do not apply to the SDMA channels.
6. DMA and SDMA read and write cycle timing is the same as that for the M68000 core.
Num.
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
DREQ Asynchronous Setup Time (see Note
1)
DREQ Width Low (see Note 2)
DREQ Low to BR Low (see Notes 3 and 4)
Clock High to BR Low (see Notes 3 and 4)
Clock High to BR High Impedance (see
Notes 3 and 4)
BGACK Low to BR High Impedance (see
Notes 3 and 4)
Clock High to BGACK Low
AS and BGACK High (the Latest One) to
BG Low to BGACK Low (No Other Bus
Master) (see Notes 3 and 4)
BR High Impedance to BG High (see Notes 3
and 4)
Clock on which BGACK Low to Clock on
which AS Low
Clock High to BGACK High
Clock Low to BGACK High Impedance
Clock High to DACK Low
Clock Low to DACK High
Clock High to DONE Low (Output)
Clock Low to DONE High Impedance
DONE Input Low to Clock Low (Asynchro-
nous Setup)
BGACK Low (when BG Is Asserted)
Characteristic
MC68302 USER’S MANUAL
t
t
Symbol
t
t
t
t
REQLBRL
t
t
t
t
CLBKLAL
BRHBGH
t
t
t
t
CHACKL
CLACKH
t
t
DNLTCH
BKLBRZ
ABHBKL
BGLBKL
t
REQASI
t
CHBRL
CHBRZ
CHBKH
CHDNL
CHBKL
CLBKZ
CLDNZ
REQL
Min
16.67 MHz
1.5
1.5
15
—
—
—
30
—
—
—
—
—
—
—
15
2
0
2
(see Figure 6-6 and Figure 6-7)
Max
+30
+30
2.5
2.5
30
30
30
30
15
30
30
30
30
—
—
—
—
—
2
2
Min
1.5
1.5
15
25
15
—
—
—
—
—
—
—
—
—
—
2
0
2
20 MHz
Electrical Characteristics
Max
+25
+25
2.5
2.5
25
25
25
25
15
25
25
25
25
—
—
—
—
—
2
2
Min
1.5
1.5
10
20
10
—
—
—
—
—
—
—
—
—
—
2
0
2
25 MHz
Max
+20
+20
2.5
2.5
20
20
20
20
10
20
20
20
20
—
—
—
—
—
2
2
Unit
clks
clks
clks
clks
clks
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
6-13