Service manual
8 163
Theory of Operation
DIGITAL CONTROL OPERATION
8. Theory of Operation
A1 CPU
The A1 CPU consists of the following circuits and parts:
CPU central processing unit that controls the analyzer.
DSP digital signal processor that is used for fast data processing.
Memory storages consists of BOOT ROMs, Flash Memory, EEPROM,
Backup SRAM, DRAM, and Dual Port SRAM. The backup
SRAM is powered from a large capacitor that is charged
when the analyzer is turned on. Therefore, the SRAM keeps
its data at least 72 hours after the analyzer is turned off. The
Dual Port SRAM is used for communication between the
CPU and DSP.
F-Bus Timer is used in the frequency bus measurement that is a diagnostic
function of the analyzer.
Analog Board Interface interfaces between the CPU and analog assemblies.
Keyboard Control controls the A30 front-panel keyboard.
Audio Interface controls the beeper on A30 front-panel keyboard.
Ethernet Control communicates with the LAN network through the LAN port
on the A34 I/O connector.
GPIB Control communicates with the external GPIB devices through the
GPIB connector on the A34 I/O connector.
mini-DIN Control interfaces between the CPU and the external keyboard
through the mini-DIN connector on the A32 I-BASIC
Interface.
I/O Control controls external devices through the I/O PORT connector
on the A32 I-BASIC interface. It also interfaces between the
CPU and the external inputs through the EXT PROG
RUN/CONT connector.
FDD Control controls the A53 FDD.
A30 Front Keyboard
The A30 front keyboard assembly detects your inputs(key inputs and RPG inputs) from the
front panel of the 4294A, and transmits them to the keyboard controller on the A1.
A32 I-BASIC Interface
The A32 I-BASIC Interface is the board with three connectors: the EXT PROG
RUN/CONT connector, the I/O PORT connector, and the mini-DIN connector. These
connectors are connected to the I/O control and mini-DIN control circuit on the A1.
A34 I/O Connector
The A34 I/O connector is the board with five connectors: the GPIB connector, the VIDEO