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HS-82C37 数据表(PDF) 25 Page - Harris Corporation

部件名 HS-82C37
功能描述  Radiation Hardened CMOS High Performance Programmable DMA Controller
Download  28 Pages
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制造商  HARRIS [Harris Corporation]
网页  http://www.harris.com
标志 HARRIS - Harris Corporation

HS-82C37 数据表(HTML) 25 Page - Harris Corporation

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25
HS-82C37ARH
Software Commands
There are special software commands which can be exe-
cuted by reading or writing to the HS-82C37ARH. These
commands do not depend on the specific data pattern on the
data bus, but are activated by the I/O operation itself. On
read type commands, the data value is not guaranteed.
These commands are:
Clear First/Last Flip-Flop: This command is executed prior
to writing or reading new address or word count information
to the HS-82C37ARH. This initializes the flip-flop to a known
state so that subsequent accesses to register contents by
the microprocessor will address upper and lower bytes in the
correct sequence.
Set First/Last Flip-Flop: This command will set the flip-flop
to select the high byte first on read and write operations to
Address and Word Count registers.
Master Clear: This software instruction has the same effect
as the hardware Reset. The Command, Status, Request,
and Temporary Registers, and Internal First/Last Flip-Flop
and Mode Register Counter are cleared and the Mask Reg-
ister is set. The HS-82C37ARH will enter the Idle cycle.
Clear Mask Register: This command clears the mask bits of
all four channels, enabling them to accept DMA requests.
Clear Mode Register Counter: Since only one address
location is available for reading the Mode Registers, an inter-
nal two-bit counter has been included to select Mode Regis-
ters during read operations. To read the Mode Registers,
first execute the Clear Mode Register Counter command,
then do consecutive reads until the desired channel is read.
Read order is channel 0 first, channel 3 last. The lower two
bits on all Mode Registers will read as ones.
External EOP Operation
The EOP pin is a bidirectional, open drain pin which may be
driven by external signals to terminate DMA operation.
Because EOP is an open drain pin an external pull-up resis-
tor is required. The value of the external pull-up resistor used
should guarantee a rise time of less than 125ns. It is impor-
tant to note that the HS-82C37ARH will not accept external
EOP signals when it is in an SI (Idle)state. The controller
must be active to latch EXT EOP. Once latched, the EXT
EOP will be acted upon during the next S2 state, unless the
HS-82C37ARH enters an Idle state first. In the latter case
the latched EOP is cleared. External EOP pulses occurring
between active DMA transfers in demand mode will not be
recognized, since the HS-82C37ARH is in an SI state.
CHANNEL
REGISTER
OPERA
TION
SIGNALS
INTERNAL
FLIP-FLOP
DATA BUS
DB0-DB7
CS
IOR
IOW
A3
A2
A1
A0
0
Base and Current
Address
Write
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
1
A0-A7
A8-A15
Current Address
Read
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
1
A0-A7
A8-A15
Base and Current Word
Count
Write
0
0
1
1
0
0
0
0
0
0
0
0
1
1
0
1
W0-W7
W8-W15
Current Word Count
Read
0
0
0
0
1
1
0
0
0
0
0
0
1
1
0
1
W0-W7
W8-W15
1
Base and Current
Address
Write
0
0
1
1
0
0
0
0
0
0
1
1
0
0
0
1
A0-A7
A8-A15
Current Address
Read
0
0
0
0
1
1
0
0
0
0
1
1
0
0
0
1
A0-A7
A8-A15
Base and Current Word
Count
Write
0
0
1
1
0
0
0
0
0
0
1
1
1
1
0
1
W0-W7
W8-W15
Current Word Count
Read
0
0
0
0
1
1
0
0
0
0
1
1
1
1
0
1
W0-W7
W8-W15
2
Base and Current
Address
Write
0
0
1
1
0
0
0
0
1
1
0
0
0
0
0
1
A0-A7
A8-A15
Current Address
Read
0
0
0
0
1
1
0
0
1
1
0
0
0
0
0
1
A0-A7
A8-A15
Base and Current Word
Count
Write
0
0
1
1
0
0
0
0
1
1
0
0
1
1
0
1
W0-W7
W8-W15
Current Word Count
Read
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
1
W0-W7
W8-W15
3
Base and Current
Address
Write
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
1
A0-A7
A8-A15
Current Address
Read
0
0
0
0
1
1
0
0
1
1
1
1
0
0
0
1
A0-A7
A8-A15
Base and Current Word
Count
Write
0
0
1
1
0
0
0
0
1
1
1
1
1
1
0
1
W0-W7
W8-W15
Current Word Count
Read
0
0
0
0
1
1
0
0
1
1
1
1
1
1
0
1
W0-W7
W8-W15
FIGURE 11. WORD COUNT AND ADDRESS REGISTER COMMAND CODES
Spec Number
518058


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