PRELIMINARYDocument type: Title: Revision date: Revision:User's Manual (MUT) Mod. V1729 4 Channel 12 Bit Sampling ADC 22/06/2005 3NPO: Filename: Number of pages: Page:00109/04:V1729.MUTx/03 V1729_REV3.DOC 38 284.6 Interfaces4.6.1 VME interfaceThe board is compatible with the A24-D16 and A32-D32 modes. It supports the h09,h0B, h0D, h0F, h39, h3B, h3D and h3F ADDRESS MODIFIERS, and therefore dealswith the accesses in block mode.The base address is given by : switch_address x h10000 (0for A24-D16 and 0The offset is given by: sub_address x h100The complete address is given by : base_address + offsetThe IRQ3 is used to signal to the acquisition system the presence of data waiting in theRAM. This interruption should be released by any writing at the address of theINTERRUPT register, which sets it back to 0. It is anyhow also reset by the START_ACQcommand.The sending of IRQ3 can be inhibited by the positioning at 1 of the INH_IRQ bit (bit 1 ofthe CONTROL_REG register).The presence of waiting data can be equally detected without treating the interruption,but by scanning the presence of a 1 in the same INTERRUPT register. However, itshould be avoided because it is a source of noise during the data acquisition.The reading of the data stored in the RAM is executed by realizing N successivereadings at the address of RAM_DATA or by realizing series of readings in block modeat this same address (blocks of 128 16-bit words or 64 32-bit words maximum to complywith the VME standard).4.6.2 GPIB InterfaceThe V1729 boards can have an address set between 0 and 29 (decimal).WritingThe GPIB commands are carried out by writing a string of characters in the boardsituated at the address designated by the rotary switches.The ASCII code of the first character corresponds to the sub-address of the order to beexecuted or of the register to be addressed.The ASCII codes of the following characters correspond to the data (only one data byteexcept in the case of a writing to the sub-address hFF).ReadingA method of reading by block was implemented to accelerate the reading by GPIB. Thereading of an element is thus executed in the following way :* Writing operation of the 4 characters (#FF)(#LSB)(#MSB)(#REG) with(#FF) : ASCII hFF code character(#LSB) : ASCII code character corresponding to the 8 lowest significant bits of thenumber of bytes to read (nbyte).(#MSB) : ASCII code character corresponding to the 8 most significant bits of the numberof bytes to read.
