Logic Levels; Theory Of Operation; General - HP 5334B Service Manual

8-68. LOGIC LEVELS
8-69. This instrument uses three types of device logic. They are:
a. Transistor-Transistor Logic (TTL).
b. Emitter-Coupled Logic. (ECL).
c. Emitter-Function Logic (EEL).
Shown below are the High and Low logic levels associated with each type of logic. The values are approximate.
Table 8-7. Logic Levels
LOGIC
STATE
+2.1v
OV to +0.8V -1.8V
+
1.5V
8-70. THEORY OF OPERATION
8-71. The theory of operation describes the general overall operation of the HP 5334B and the operation of
each block assembly (circuit) located on the A1 Main board, the A2 Front Panel board, and the Option 010
Oven Oscillator plug-in module.
8-72. General
8-73. The overall operation of the HP 5334B is shown in the block diagram, Figure 8-18. The Counter uses
three microcomputers (MCU): the Executive MCU for overall control, the Measurement MCU for control of
measurement functions, and the HP-IB MCU for control of system interface functions. Each MCU carries out
its routines under the direction of its own internally stored program. The overall operation of the counter
depends on the continuous interaction of the Multiple-Register Counter (MRC)
,
described in the next
paragraph, and the controlling MCU system which centers around the Executive, and Measurement MCUs.
8-74. The MCU system contains the processor, the counter operating program (ROM), and memory space
(RAM). The Multiple-Register-Counter (MRC), referred to as a "counter-on-a-chip", is a Large-Scale Integra-
tion (LSI) circuit which contains the counting registers used to accumulate the raw input measurement data. The
microcomputer system contains the processor, the counter operating program (ROM), and memory space
(RAM).
8-75. Inputs to Channel A and/or B are routed through signal conditioning circuits which perform the operator
selections of coupling, impedance, and attenuation. These signals are directed to the MRC, where they are ac-
cumulated in registers, counted, and stored as raw measurement data. The data is then retrieved by the
microcomputer system, manipulated to achieve the desired measurement mode, and routed to the display.
8-76. The Time Base is used as the reference for the counting done by the MRC. An interpolating technique is
used that divides up the time between the reference oscillator pulses and allows the MRC to count much finer
resolution.
8-77. For a typical measurement, the MCU system reads the MRC registers, reads the interpolator counters,
performs the necessary calculations, and displays the result.
HP 5334B
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Service Manual
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