spec - Local Sector 7 web page

CAMAC, GPIB and SerialBesides the built-in hardware support for moving motors and counting using CAMAC(IEEE-583), GPIB (IEEE-488) and serial (RS-232C) interfaces, spec provides generalizedinput /output support over these interfaces from the command level.The ca_get(device, subaddress) command will return the contents of theaddressed module register (F=0 in the standard FNA CAMAC command code), whileca_put(data, device, subaddress) will write the 24-bit value data to theaddressed module register (F=16). The device argument is the I /O module indexfrom the configuration file and can be 0, 1 or 2. The CAMAC slot number of the moduleis set in the configuration file. The subaddress argument is the module’s subaddress(the A in the FNA).spec allows you to send a string of characters to a GPIB instrument at any GPIBaddress and to read a string of characters from any instrument. When reading characters,spec will accept a string terminated by either a newline or by carriagereturn—newline, or you can specify the number of bytes to be read. For example, toinitialize a particular voltmeter having GPIB address 12, you would issue the command:73.FOURC> gpib_put(12, "D0R0Z0B0T0K1M0G1X")74.FOURC>That instrument might then be read with:74.FOURC> {k_ohms = gpib_get(12); print k_ohms}100.02475.FOURC>The command75.FOURC> x = gpib_get(12, 4)76.FOURC>would read 4 bytes from device 12 and not look for terminators.When sending strings using gpib_put() ,you cannot send null bytes. Usually adevice that requires null lower order bits in a data byte will ignore the high order(parity) bit. In this case, you can usually set that highest bit to avoid sending a nullbyte.The ser_get(device, n) and ser_put(device, string) functions access the serialinterface, where device is the index from the configuration file and can be 0, 1 or 2.In ser_get() , n is the most number of bytes to read. The function will return afterreading one line (terminated by a newline or carriage return) from the device, even if34 USER MANUAL AND TUTORIALS INTERIM WORK-IN-PROGRESS (8/16/01) NOT FOR GENERAL DISTRIBUTION