HP 16500B Microprocessor Board Theory, Microprocessor and System ROM & RAM, Interrupt Control

Theory of Operation

The Microprocessor Board

Microprocessor Board Theory

The microprocessor board contains the system memory, all of the interfaces for the mainframe peripherals, the intermodule bus monitor, and the option board module interface.

Microprocessor and System ROM & RAM

The processing engine of the HP 16500B microprocessor board is a Motorola 68EC030 microprocessor. The 68EC030 is supported by 128 Kbytes of ROM and 8 Mbytes of single inline memory module (SIMM) RAM. Stored in ROM are the power-up routines for the mainframe including the power-up self tests and the disk drive instructions. The HIL driver is also resident in system ROM.

Supply Voltage Supervisor

The Supply Voltage Supervisor (SVS) monitors the main power supply bus and ensures a smooth power-up of the microprocessor system. The SVS also ensures a graceful recovery of the system in case the line voltage drops below nominal levels.

During power-up, the SVS asserts the microprocessor L_RESET pin when the supply voltage stabilizes. Because the voltage on the main power supply bus is affected by abnormal line voltages, the SVS asserts the microprocessor L_HALT pin during a low line voltage condition. When the line voltage returns to a nominal value, the L_RESET pin is then asserted by the SVS and the HP 16500B will reboot.

Interrupt Control

The Interrupt Control circuit manages the interrupt signals asserted by the peripheral devices. When an interrupt is received, the Interrupt Control circuit encodes the interrupt signal from the peripheral device to the microprocessor as a prioritized microprocessor interrupt.

Address Area Decoder and Peripheral Decoder

The mainframe peripheral interfaces link the microprocessor data and address busses with the system peripherals. The system peripherals are then selected by the microprocessor through the address area decoder and peripheral decoder. The peripheral decoder selects all peripherals including the HIL interface, the HP-IB and RS-232C interfaces, the color palette, the hard disk drive interface, and the flexible disk drive interface. The address area decoder enables access to system ROM, the display RAM, peripherals, and the HP 16500L interface module.

Real Time Clock

The Real Time Clock provides time information to the HP 16500B microprocessor system. The time information is used to place a time stamp on files stored on both the hard and flexible disk drives. Time information may also be used by certain option modules to time stamp acquired data. For more information regarding the option modules, refer to the User’s Guide of the specific module.

Ethernet LAN Interface

Using line drivers, the Ethernet LAN Interface links the microprocessor address and data bus with the LAN controller IC on the HP 16500L Interface Module. Consult the HP 16500L Administrator’s and Service Guide for more information regarding the HP 16500L Interface Module.

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