HP 35601A Operating And Service Manual

Model 35601A ServiceAfter start-up, RFD is normally set high ('NRFD' = 1) and DAC is set low ('NDAC =0);this is state 10 in Figure 6-26. When the HP-IB talker sees this, it will put data on lines'Dior through 'DI08\ wait for the lines to settle, then set DAV high (the HP-IB line'DAV = 0). When the handshake circuitry sees DAV = 1, it will go to state 00, set RFD low,and trigger MONOl. After 0.5G sec, MONOl will trigger MON02. If DAV is still high, thecircuitry will go to state 01; it will keep RFD low and set Q2 high. MON02 will generate thelatch pulse to either U17 or one of the control latches depending on the state of DI08. At theend of MON02, the data has been latched, so 'NDAC is set high. When the listener seesthis, it makes 'DAV'(the HP-IB line) high; DAV (U29 pin 8) goes low. When the circuitrysees DAV go low, it returns to state 10 via state 00. At this point, the handshake is ready foranother cycle.NOTEThe latch pulse is only allowed when DAV is true and ATN isfalse, as determined by U22B and U22A. At start-up, the boardwill go to state 01 if DA V is true. This case should never exist, butis defined to avoid any system hang-up.6 81. Addressing the A1 Board.Addressing to listen occurs when the talker sets the Listen Flip-Flop. First, the talker sets'ATN' true (low) and 'DI01' through 'DI05' to the address of the -hp- 35601 A. 'DI06' isset true, and 'DI07' is set false; this is HP-IB convention. The Al Board compares the dataon the 'Dior through 'DI05' to the address of the -hp- address. This is accomplished withU23 and U31 which also checks that '0106' is true. U29A checks that '0107' is false. If atrue comparison exists, U31 pin 6 gets high, (far out) When an address comparison exists,and DAV is set true with ATN true, as determined by U29B, the address flip-flop (FF3) willbe set by a pulse from MON02 to U29A pin 2.The Al board can be unaddressed in three ways:1. At start-up with a reset pulse.2. By 'IFC being set true by the talker.3. When the unlisten command is sent. This is detected by U30.When the board has been addressed to listen, LED CRl is turned on by U21E and the frontpanel ADDRESSED indicator is turned on by U21F. If SWl is set to REMOTE and theboard is unaddressed, the data lines to the control latches are disabled by U25D. This is doneto prevent digital noise from leaking to the rest of the instrument because of poor isolationfrom the control latches. The control latches have a different power supply for the samereason.6-73