a8237

®
Programmable
DMA Controller
April 1999, ver. 1.01 Data Sheet
Features
n a8237 MegaCore function implementing a programmable direct
memory access (DMA) controller
n Optimized for FLEX
®
architecture
n Provides four independent channels
n Offers static read/write or handshaking modes
n Includes direct bit set/reset capability
n Uses approximately 1,201 FLEX logic elements (LEs)
n Functionally based on the Intel 8237A and Harris 82C37A devices,
except as noted in “Variations & Clarifications” on page 24
General
Description
The a8237 MegaCore function implements a programmable DMA
controller, which controls memory-to-peripheral and memory-to-
memory data transfers and provides block memory initialization
capability. Four independently programmable channels are available in
the a8237, and DMA requests can be made via hardware or software.
Figure 1 shows the symbol for the a8237.
Figure 1. a8237 Symbol
clk
hlda
ncs
neopin
niorin
niowin
ready
reset
ain[3..0]
dbin[7..0]
dreq[3..0]
adstb
aen
dben
dmaenable
hrq
neopout
niorout
niowout
nmemr
nmemw
aout[7..0]
dack[3..0]
dbout[7..0]
A8237
Altera Corporation 5
A-DS-A8237-01.01