5-16 Service Guide N5227-90001
Theory of Operation PNA Series Microwave Network Analyzers
Synthesized Source Group Operation N5227A
Rear-Panel Interconnects
A23 Test Set Motherboard
The A23 test set motherboard serves these functions:
• to act as an interface between the A21 CPU board and the auxiliary rear panel interconnects.
• to provide ALC signals to the A25 HMA26.5.
• to route control signals to the signal separation group. Refer to “Signal Separation Group Operation” on
page 5-20 for more information.
Rear Panel Interconnects
The A23 test set motherboard includes the following rear panel interconnects.
10 MHz REF INPUT A BNC connector that allows an external frequency reference signal to be used
to phase lock the analyzer for increased frequency accuracy.
The analyzer automatically enables the external frequency reference feature
when a signal is connected to this input. When the signal is removed, the
analyzer automatically switches back to its internal frequency reference.
10 MHz REF OUTPUT A BNC connector that allows a 10 MHz reference signal, produced by the A14
frequency reference board, to be output for use in phase locking external test
equipment.
TEST SET I/O A DB-25 female connector that is used to control external test sets. The external test set
bus consists of 13 multiplexed address and data lines, three control lines, and an
open-collector interrupt line. Pin assignments are listed in Table 5-2 on page 5-17.
Up to 16 test sets may be “daisy-chained” on the bus at one time.
The Test Set I/O is not compatible with 8753 network analyzer test sets.
HANDLER I/O A rectangular 36-pin, female connector providing four independent parallel input/output
ports, nine control signal lines, one ground, and a power supply line. This connector has
Type 2 output pin assignments as listed in Table 5-3 on page 5-18.
All signals are TTL-compatible. Data input/output ports consist of two 8-bit output ports
(Port A and Port B) and two 4-bit bidirectional ports (Port C and Port D).
Connector settings can be changed using SCPI and COM commands. The settings are not
accessible from the front panel.
PWR I/O A DB-9 female connector. Pin assignments are listed in Table 5-4 on page 5-19.
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