Electrical and Computer Engineering ETDs

Publication Date



A Microprogramned Branch Driver (MBD) is the interface between Digital Equipment Corporation (DEC) PDP-11 series computers and a multicrate CAMAC system. The MBD is a microprocessor-controlled multiple, direct memory access (DMA) channel branch driver.

The requirements for an MBD are discussed in the introduction and stem from a Los Alamos Scientific Laboratory (LASL) study group report on the design of the Clinton P. Anderson Meson Physics Facility (LAMPF) data acquisition system. Because of the desire for the standard system, the types of experiments and data rates, and the varying complexity of the data acquisition systems, it was decided that a microprogrammable, multiple OMA channel branch driver was required. A brief description of CAMAC is presented to help understand the operation and the design of the MBD.

The design section is limited to system design, the trade-offs between cost and capabilities, and the decisions that led to the final design. The PDP-11 computer interface requirements and the CAMAC Branch Highway interface requirements dictated a sizable amount of the MBD design. The balance of the design was determined by the fact that a microprocessor with a read-write control memory was desired.

To facilitate checkout, and to serve as a manual controller when the MBD was used as a stand-alone branch driver, a PDP-11 simulator (separate unit) was designed and fabricated. A control panel option was designed to simplify and speed up the loading of the bootstrap loader for a stand-alone system. After manually loading the bootstrap, the control programs could be loaded from a teletype, paper tape reader, data link, etc.

The basic operation and capabilities of the MBD are discussed in the operation section. The discussion includes the modes of operation, the registers of the MBD, the instruction set, the priority structure, the interrupts, the operation of the OMA channels, and the branch driver section. The section includes programs to load the MBD memory from the PDP-11, to initialize the channels, and control programs.

The last section summarizes the performance specifications. This includes the hardware and options, the power requirements, operating speeds, temperature ranges, documentation, and software package.

Document Type




Degree Name

Computer Engineering

Level of Degree


Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Dale Sparks

Second Committee Member

Lara Henry Baker

Third Committee Member

Bruce Richard Peterson