CMOS MT8920B
CHANNEL N - BIT 0
CHANNEL (N + 1) - BIT 7
ST-BUS ACCESS
CONTENTION WINDOW
C4i
(N matches incoming
ST-BUS channel)
A0 - A5
READ ADDRESS N or WRITE ADDRESS (N + 1)
CS
CONDITION 1:
Access begins before contention window and finishes before ST-BUS access - No contention.
OE, R/W
BUSY
t
EC4H
CONDITION 2:
OE, R/W
Access begins before contention window and continues into ST-BUS access.
t
EC4L
t
t
C4BH
C4BL
BUSY
Access begins within contention window but before ST-BUS access.
CONDITION 3:
OE, R/W
t
EC4L
t
C4BH
t
EBL
BUSY
CONDITION 4:
OE, R/W
Access begins during ST-BUS access
t
C4BH
t
EBL
BUSY
Figure 16 - Mode 2 Access Contention Resolution
3-21