COM20022I Datasheet, PDF (23/83 Pages) SMSC Corporation – 10 MBPS ARCNET 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:
nDACK becomes active (low) upon DREQ becoming active (high) and catching the host bus (AEN=1).
DREQ becomes inactive after nDACK and read/write signal become active.
DREQ becomes active after nDACK or read/write signal becomes inactive.
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.
nDACK becomes inactive after DREQ=0 and the present cycle finishes.
SMSC COM20022I
Page 23
DATASHEET
Rev. 08-18-03