M-CAS-C8237 Datasheet, PDF (3/5 Pages) Altera Corporation – PROGRAMMABLE DMA CONTROLLER ALTERA CORE

Request Register
Write Request Register Command:
A3 A2 A1 A0 IORN IOWN
10011
0
Each channel has a request bit associated with it in the 4-bit
Request register. These are non-maskable and subject to pri-
oritization by the Priority Encoder. Each register bit is set or
reset separately under software control or is cleared upon
generation of a TC or external EOPN. The entire register is
cleared by a Reset. In order to make a software request, the
channel must be in Block Mode.
X X X X X D2 D1 D0
Bit1 & Bit0: 00 -> Channel 0
01 -> Channel 1
10 -> Channel 2
11 -> Channel 3
Bit2: 0 -> Reset request bit
1 -> Set request bit
Mask Register
Each channel has a mask bit associated with it which can be
set to disable the incoming DREQ. Each mask bit is set when
its associated channel produces an EOPN if the channel is
not programmed for Auto initialize. Each bit of the 4-bit Mask
register may also be set or cleared separately under software
control. The entire register is also set by a Reset. This dis-
ables all DMA requests until a clear Mask register instruction
allows them to occur.
Programming All Mask Register Bits:
Write All Mask Register Bits Command:
A3 A2 A1 A0 IORN IOWN
11111
0
X X X X X D2 D1 D0
Bit1 & Bit0: 00 -> Channel 0
01 -> Channel 1
10 -> Channel 2
11 -> Channel 3
Bit2: 0 -> Clear mask bit
1 -> Set mask bit
Programming Single Mask Register Bits:
Write Single Mask Register Bit Command:
A3 A2 A1 A0 IORN IOWN
10101
0
X X X X D3 D2 D1 D0
Bit0: 0 -> Clear channel 0 mask bit
1 -> Set channel 0 mask bit
Bit1: 0 -> Clear channel 1 mask bit
1 -> Set channel 1 mask bit
Bit2: 0 -> Clear channel 2-mask bit
1 -> Set channel 2 mask bit
Bit3: 0 -> Clear channel 3-mask bit
1 -> Set channel 3 mask bit
Status Register
Read Status Register Command:
A3 A2 A1 A0 IORN IOWN
10000
1
This register is available to be read out of the C8237 by the
microprocessor. It contains information about the status of the
devices at this point. Bits 0-3 are set when that channel
reaches a TC or an external EOPN is applied. These bits are
cleared upon Reset and on each Status Read. Bits 4-7 are
set whenever their corresponding channel is requesting.
D7 D6 D5 D4 D3 D2 D1 D0
Bit0: 1 -> Channel 0 has reached TC
Bit1: 1 -> Channel 1 has reached TC
Bit2: 1 -> Channel 2 has reached TC
Bit3: 1 -> Channel 3 has reached TC
Bit4: 1 -> Channel 0 request
Bit5: 1 -> Channel 1 request
Bit6: 1 -> Channel 2 request
Bit7: 1 -> Channel 3 request
Cast, Inc.
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