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==========================================
 HP3562A Dynamic Signal Analyzer - Part 2
==========================================

:Author: David Douard
:Category: Electronics
:Tags: HP3562A, repair, test equipment, DSA
:series: HP 3562A
:series_index: 2

This is the part 2 of the series about my
`HP 3562A Digital Signal Analyzer <{filename}hp3562a.rst>`_,
quickly describing the Digital Section of the instrument.


Digital Section
===============

The unit is quite capable, since the main CPU is a 68000 (not exactly
of small CPU for the time).

.. image:: {filename}images/hp3562a/cpu.jpg

The 8 boards are:

- A1: Digital source and front-end interface (rev B, ref: 03562-66501) 
- A2: CPU & GPIB controller (rev D, ref: 03562-66502)
- A3: Memory (rev B, ref: 03562-66538)
- A4: Local oscillator (rev C, ref: 03562-66504)
- A5: Digital filter (rev B, ref: 03562-66505)
- A6: Digital filter controller (rev D, ref: 03562-66506)
- A7: Floating Point Processor (FPP) (rev B, ref: 03562-66507)
- A9: FFT (rev B, ref: 03562-66509)

The service manual also describes an A8 board with additional RAM, but
my device does not have such a board. It looks to me that my version
of the DSA has both extra ROM and RAM on the A3 memory board.


Digital Source
--------------

.. Note:: The Service Manual available on the net lacks a few pages in
          the Digital Source section, so I do not have details on the
          Timing Control section.

.. image:: {filename}images/hp3562a/hp3562a_a1_block_diagram.png
   :alt: Block diagram of the A1 Digital Source Board

This board is mainly responsible for generating the digital signals
that are used as input for the source DAC. It generates all sort of
noise figures, bursts, sweeps, and so on.

.. image:: {filename}images/hp3562a/a1_digital_source.jpg

The Timing Control section looks like:

.. image:: {filename}images/hp3562a/hp3562a_a1_timing_control_circuit.png
   :alt: A1 Timing Control block diagram

The Phase Resolution is used in external and internal triggered
measurements, ensuring that the phase of a triggered measurement is
accurate. Since the trigger moment does not always occur on a sample
and hold edge, there is a time delay and phase error in the data.
This phase resolution circuit counts the time between the samples and
a trigger.

.. image:: {filename}images/hp3562a/hp3562a_a1_phase_resolution_circuit.png
   :alt: A1 Phase Resolution block diagram

The Burst Control circuit controls the burst length and generates the
pulse signal to the Local Oscillator (A4). It provides the gating
signal that gates the analog source on and off during the burst and
chirp modes.

.. image:: {filename}images/hp3562a/hp3562a_a1_burst_control_circuit.png
   :alt: A1 Burst Control block diagram


Other parts of this board are the LO Input Receiver that synchronizes
the local oscillator input data to the sample rate, the Multiplier
that multiply the LO data by the noise and send it to the analog
source, and the Noise Generator that produces binary random sequences
that is used for band-limited random noise and burst noise signals.


CPU
---

The processing unit is a MC68000. It aims at telling each assembly
which process to execute and monitor the overall functionning and data
processing of the instrument.

.. image:: {filename}images/hp3562a/hp3562a_a2_block_diagram.png

The main CPU board, with the beautiful MC68000P9 DIP64 package:

.. image:: {filename}images/hp3562a/a2_cpu.jpg

It comes with 2 populated M5M256BP static ram chips (32k x 8bits), for
the CPU, but seems to be capable of holding 4 more of them. The CPU
runs at 8MHz.

There is also some ROM, the main "boot loader" program. Unfortunately,
neither of the ROM chips are mounted on sockets but are directly
soldered on the PCBs, so I did not took the risk of damaging one of
them by desoldering them for dumping their content.

Most of the remaining of the circuit is to manage the global data bus,
the system bus, the IRQs and the GPIB bus.

The blue connector is for the GPIB connector.


Memory
------

.. image:: {filename}images/hp3562a/a38_memory.jpg

This board is described as an "extension of the read only memory of
the system CPU board" and read/write memory used by most of the other
assemblies.

.. image:: {filename}images/hp3562a/hp3562a_a38_memory_block_diagram.png

The ROM section stores most programs for the HP 3562A except the
startup routines (which are on the ROM ships of the A2 CPU
bloard).

The board allows flexibility in the number and type of ROM chipes
used. ROM density is selected by placement of jumpers.

.. image:: {filename}images/hp3562a/hp3562a_a38_rom_block_diagram.png


The RAM section of the assembly consist of 4 32k by 8 bits static RAM
chips as well as the arbitrer section which controls access requests
to the global RAM from six devices (FFT, both Digital Filters,
Display, FPP and the system CPU).
	   
.. image:: {filename}images/hp3562a/hp3562a_a38_ram_block_diagram.png

The Display Controller section also lies on this A38 board.
	   
.. Note:: On older versions of the instruments, this board was
	  splitted in 2 (A3 and A8) and used less dense chips (thus, much more
	  chips).


Local Oscillator
----------------

The Local Oscillator produces digital sin and cosine signals
(synchronized with the sample rate). The sinusoidal signal is
generated from a table of values stored in the ROM.

.. image:: {filename}images/hp3562a/hp3562a_a4_block_diagram.png

.. image:: {filename}images/hp3562a/a4_loc.jpg



Digital Filter and Digital Filter Controller
--------------------------------------------

The Digital Filter Assembly consists in both A5 and A6. It processes
two channels of serial data coming from the instrument front end (ADC)
ans stores the results in global RAM. Processing consists of
conversion from a serial format to a parallel format and, if required,
digital filtering or zoom (a combination of frequency shifting and
filtering). The processed data is transferred on the global data bus.

.. figure:: {filename}images/hp3562a/a5_a6_block_diagram.png
   :alt: Digital Filter Assembly block diagram

   Digital Filter Assembly block diagram.
	 
**Digital Filter:** Each digital filter consists of a control IC and 2
filter ICs, one for the real data and one for the imaginary data.
   
.. figure:: {filename}images/hp3562a/a6_zoom.png
   :alt: Digital Filter for the zoom mode

   The Digital Filters are fed with a kind of LF I/Q demodulator, used
   for zooming or actual digital filtering.


.. figure:: {filename}images/hp3562a/a5_filter.jpg
   :alt: Picture of the A5 Digital Filter board

   Picture of the A5 Digital Filter board.

.. figure:: {filename}images/hp3562a/hp3562a_a5_block_diagram.png
   :alt: Digital Filter block diagram

   The A5 Digital Filter board block diagram.


**Clock Generator:** The clock generator creates two complementary clock
pulses from the 10.24MHz system clock.

**Overload Detect:** The first 3 bits in the ADC serial data stream
contain overrange information that must be stripped off the serial
data.

   
.. figure:: {filename}images/hp3562a/a6_control.jpg
   :alt: Picture of the A6 Digital Filter Control board

   Picture of the A6 Digital Filter Control board.

.. figure:: {filename}images/hp3562a/a6_block_diagram.png
   :alt: Digital Filter Controller block diagram

   The A6 Digital Filter Controller board block diagram.


FPP
---

The Floating Point Processor board is a fast arithmetic unit which
carries out real and complex arithmetic operations on blocks of data
stored in the global RAM. The processing ALUs are six AM2903 bit-slice
microprocessor ICs and one AM2910 microprogram
controller. Instructions are provided to the ALUs by an address
sequencer and seven microcode PROMs.

.. figure:: {filename}images/hp3562a/hp3562a_a7_block_diagram.png
   :alt: Floating Point Processor block diagram
   :align: center
	   
   Floating Point Processor block diagram.
      
.. figure:: {filename}images/hp3562a/a7_fpp.jpg
   :alt: Picture of the A7 FPP board 
   :align: center

   Picture of the A7 FPP board.
	   
This Floating Point Processor is capable of handling 16 bits integers,
32 bits and 64 bits floats.


FFT
---

.. image:: {filename}images/hp3562a/hp3562a_a9_block_diagram.png

The FFT board performs windowing, FFT and Inverse FFT directly from
and to the RAM.
It's built around a TMS230 microprocessor runningat 5MHz

.. image:: {filename}images/hp3562a/a9_fft.jpg


Keyboard
--------

.. image:: {filename}images/hp3562a/hp3562a_a15_block_diagram.png


Next
====

In the `next part <{filename}hp3562a_3.rst>`_, we will describe the
Analog Section of the instrument.