Interfacing An Mc68Ec020 To A Dma Device That - Motorola MC68020 User Manual

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.
MC68EC020
MOTOROLA
BR
BG
BGACK
(DMA)
74LS04
BR
(DMA)
74LS04
BG
(MC68EC020)
Figure A-1. Bus Arbitration Circuit—
MC68EC020 (Two-Wire) to DMA (Three-Wire)
M68020 USER'S MANUAL
74LS08
BR
(MC68EC020)
4
PR
BG
D Q
(DMA)
74F74
CLK
Q
CLR
+5 V
BR
BG DMA
BGACK
A- 1