National Instruments GPIB-PC - Manual (Page 93)

BASICA/QuickBASIC GPIB-PC Function Calls Section Four A
GPIB-PC User Manual 4A-18 ©National Instruments Corp.
2. Take control synchronously and assert ATN following a read
operation.
100 CALL IBRD (BRD0%,RD$)
110 V% = 1
120 CALL IBCAC (BRD0%,V%)