HP 70427A User Manual page 507

Overview
Looking at the Block
Diagram
Block Diagram
Controller, I/O Interface and Power Supply Assembly A6
Controller, I/O Interface and Power Supply
Assembly A6
The A6 assembly is composed of two printed circuit boards (PCBs). The
controller board contains the microprocessor, HP-IB interface and the
MS-IB interface. The I/O and power supply board contains the digital
control chip drivers, the drivers for two YTF assemblies, the internal
voltmeter, the module's eight power supplies and the power supply/digital
control distribution which supply all the other assemblies.
Digital Controller
The digital control unit (DCU) uses a Motorola MC68HC000R8
microprocessor IC running at an 8 MHz clock rate. 1 Mbyte of erasable
programmable read-only-memory (EPROM) and 128 kbytes of
random-access-memory (RAM) are provided, along with HP-IB and MS-IB
interfaces. A Motorola MC68901 Multi-function Peripheral IC provides
timers, a serial port (not used in the firmware), and an interrupt controller. In
addition, two 8-bit DIP switches, a number of LED drivers and parallel I/O
interfacing to the I/O interface/power supply assembly are provided. The
microprocessor also has 2048 bytes of electronically erasable programmable
read only memory (EE- PROM) for calibration data storage.
The firmware for the entire HP 7042x family of modules is resident in the
EPROMS on the controller PCB. The firmware is written as a series of
virtual modules allowing the user to access all the functions built into his
module. Example: the HP 70427A will function as an HP 70427A
downconverter or as an HP 70428A source, since the HP 70428A function is
needed for the downconverter function. Also, the HP 70428A Option 002
will function as an HP 70428A Option 002 upconverter or an HP 70428A
source. A softkey on the MMS display, or an HP-IB command is used to
switch between the virtual modules available.
The module's hardware configuration is stored in the EE-PROM at the
factory along with the required calibration data needed for proper module
operation.
I/O Interface
The I/O interface converts parallel I/O information to and from the controller
board into the serial data needed to drive the serial interfaces throughout the
module. It also converts the 6-bit parallel information needed to drive two
YTF driver assemblies.
13-72 HP 70427A/HP 70428A User's Guide