Anritsu 37 D Series, Руководство по обслуживанию, Страница: 57 / 190

q System boot-up EPROM—This chip contains the boot-up instruc-
tions used by the system CPU at power-up.
A13 I/O Interface #1
PCB Assembly
This PCB assembly performs the following functions:
q Floppy drive control—interface for the Floppy Drive Assembly
q External Keyboard control—interface for the front panel
Keyboard connector
q Interface for the A18 Rear Panel PCB Assembly (below)
q Interface and control for the rear panel IEEE 488.2 GPIB and
Dedicated GPIB interface connectors
A14 I/O Interface #2
PCB Assembly
This PCB assembly contains a State Machine controller, decode logic,
and bus interface control circuits that perform the following functions:
q
Quiet Bus interface control—The Quiet Bus passes control and
data signals from the A9 Main Processor PCB to the A1 through
A8, and A21 PCBs and returns status and data signals back to
the A9 PCB. This bus is managed by the control circuits on the
A14 PCB such that it is inactive during the the time that a mea-
surement is being taken.
NOTE
The output data from the A5 PCB A/D converter is sent to the
A9 Main Processor PCB via the Quiet Bus, the A14 PCB, and
the VME Bus.
q
A/D Bus interface control—During the measurement process, all
A/D selection and conversion functions on the A5 PCB are con-
trolled exclusively by the A14 PCB State Machine Controller.
This is accomplished via the command lines of the A/D Bus.
q
Measurement control functions—the A14 PCB State Machine
Controller manages many of the VNA functions during a mea-
surement, as follows:
n
Quiet Bus interface control
n
A/D Bus interface control:
q
Sample and Hold control for A5 PCB
q
A/D selection and conversion control for A5 PCB
n
Check for phase lock condition
n
Gain ranging
n
Delay generation for IF Bandwidth setting function
The A14 PCB also provides the interface to the Front Panel A19 and
A20 PCBs.
THEORY OF OPERATION DIGITAL SUBSYSTEM ASSEMBLIES
37XXXD MM 3-21