HP 3000 Series Installation And Service Manual

Principles of cperationparallel from the INP Microprocessor and convert them into acontinuous serial stream for transmission. Simultaneously, they·can receive a serial stream of data and control information andassemble it into a series of parallel data bytes for the INPMicrop rocessor.4-7. Communication Line InterfacesThe communication line interfaces,Direct-connect, etc., translatesignals that are electrically andthe respective standards.4-8. FUNCTIONAL-LEVEL OPERATIONsuch as RS232C, Bell DDS,data and control lines intomechanically compatible withIn the following typical message transmission sequence, a moderntelephone line is assumed as the communications medium. Refer-ences are made to the functional areas, data paths, and servicerequest paths within the block diagram in figure4-1. The data paths and service request paths being referencedare identified in the diagram by circled numbers.Initially, the HP 3000 has been powered up, and the previouslyattached communication line is not yet operational. The processof powering up invokes the ROM-resident control program. Thecontrol program both resets the INP logic and verifies INP opera-tion. The results of the operation verification are available tothe HP 3000 on request.To initiate transmission, the system issues a control parameterover the Hewlett-Packard Interface Bus (HP-IB) to the HP-IBInterface of the INP, (1) • This action causes an interrupt bitto be set, (2) , which interrupts the INP Microprocessor, (3)The INP Microprocessor then reads the interrupt register, (4) ,to determine which device is requesting service. Next, the INPMicroprocessor interrogates the HP-IB Interface, (5) , todetermine the nature of the service being requested (new controlword, new data word, etc.).In this example, the control word read in (5) tells the INPmicroprocessor to start transferring data words from the HP-IBInter face to the INP RAM for local buffer ing. Typically, the INPreads a whole buffer or block from the HP 3000 before beginningto transfer data over the data communication line.The flows from the HP 3000 into memory are represented by (6)and (7) in figure 4-1. Upon receiving a full block, the INPMicrop rocessor raises RTS, (8), and sets up an interrupt forwhen the modem returns CTS. When CTS becomes active, an inter-rupt is generated to the INP Microprocessor, (9) • The INPMicroprocessor then sends data from the INP RAM to the datacomm4-4