MC68020 Motorola, MC68020 Datasheet - Page 300

• Manufacturer Part Number: MC68020
• Description: (MC68020 / MC68EC020) MICROPROCESSORS USERS MANUAL
• Manufacturer: Motorola

APPENDIX A
INTERFACING AN MC68EC020 TO A DMA DEVICE
THAT SUPPORTS A THREE-WIRE BUS ARBITRATION
PROTOCOL
The MC68EC020 supports a two-wire bus arbitration protocol; however, it may become
necessary to interface the MC68EC020 to a device that supports a three-wire arbitration
protocol. Figure A-1 shows a method by which this can be achieved.
MOTOROLA
MC68EC020
MC68EC020 (Two-Wire) to DMA (Three-Wire)
BGACK
BR
(DMA)
BG
(MC68EC020)
(DMA)
Figure A-1. Bus Arbitration Circuit—
BR
BG
74LS04
M68020 USER’S MANUAL
74LS04
D
CLK
74LS08
74F74
CLR
PR
4
+5 V
Q
Q
BR
(MC68EC020)
BG
(DMA)
BR
BG
BGACK
DMA
A- 1