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DOC E10523 Rev.D
Interactive Circuits And Systems Ltd. 2000
26
7. Set DCSR<0>. This is the 'DMAGO' bit. The transfer will start at this point.
8. At the completion of the transfer DMAGO will be read as clear. The DONE bit,
DCSR<1>, should be read as set, and a VME interrupt will be asserted. The user
should clear DCSR<1> in order to clear the interrupt. If a completion interrupt occurs
but the DONE bit is not read as set, an error has occurred. The type of error is
indicated by bits DCSR<3:2> and DCSR<5>.
5.3.2 VMEbus DMA Slave
When performing a VMEbus BLT or MBLT block transfer with the ICS-130 as the slave
device, no set-up activity is necessary unless the programmer wishes to use A64 address
cycles. The set-up procedure for doing this is given in section 5.3 above.
The maximum possible block transfer is 256KB. When initiating a transfer, the programmer
should ensure that there are sufficient samples available in the buffer, and that the buffer is
of sufficient size for the size of transfer contemplated.
5.4 ADC Data
This section of the ICS-130's VMEbus memory map is used to read data from the ADC
memory over the VMEbus. The VMEbus ADC Data area is 0x40000 bytes (256KB) in size.
The ADC memory buffers are strictly read only. The same area of the memory map allows
test pattern data to be written to the diagnostic FIFO, which is strictly write only. See section
5.16 for details on using built in diagnostics.
The data is organized as one sample in each 16-bit word, with "big endian" ordering. i.e.
odd channels occupy the most significant 16 bits and even channels occupy the least
significant 16 bits of a 32 bit longword. Channels are numbered from 1 to 32.
The data area appears to the user as FIFO type memory. In other words, random access to
samples in the memory is not available. Data access is always sequential regardless of the
address used for read or write, as long as the address used falls within the ADC Data area.
Each time a data word is read from the buffer, the data is removed from memory and buffer
pointers are modified. The user must be careful to read the exact number of 32-bit words
corresponding to the programmed buffer length, otherwise buffer overflow or underflow will
occur.
The user should perform a reset of the memory (ADC Reset register) after programming the
ADC configuration and before enabling acquisition. This is necessary to ensure that the
buffer pointers are correctly aligned prior to buffer access by the ADC circuits.
Addresses presented by the bus master when reading data may be either incremental or
repetitive (i.e. always the same address). Provided that addresses fall within the ADC Data
Содержание ICS-130
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