COM20022I_06 Datasheet, PDF (22/82 Pages) SMSC Corporation – 10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM

10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM
Datasheet
DREQ
(Active-High)
nDACK
(Active-Low)
Gate
Time
Transfer term
(Counting Read/Write pulse
or counting internal timer)
Restart
Transfer
Figure 5.4 - Programmable Burst Mode DMA Transfer (Rough Timing)
The timing of the Non-Burst mode DMA data transfer is found in the Timing Diagrams section of this data
sheet. The basic sequence of operation is as follows:
ƒ nDACK becomes active (low) upon DREQ becoming active (high) and catching the host bus (AEN=1).
ƒ DREQ becomes inactive after nDACK and read/write signal become active.
ƒ DREQ becomes active after nDACK or read/write signal becomes inactive.
ƒ DREQ becomes inactive after TC and the read/write signal assert (when nDACK=0). In this case,
DREQ doesn't become active again after nDACK becomes inactive.
ƒ nDACK becomes inactive after DREQ=0 and the present cycle finishes.
Revision 02-27-06
Page 22
DATASHEET
SMSC COM20022I