Lexicon LXP-5 Service Manual

LXP-5 Service Manual
Circuit
Description
The LXP-5 utilizes two Z80 microprocessors and the Lexchip digital signal
processor to perform multiple digital audio effects which are controlled via
three front-panel selections, as well as a serial MIDI interface. Each proces¬
sor has its own support circuitry, data and address buses. Communication
between processors is performed via two interfaces.The Master/Slave Inter¬
face allows Master Z80 access to the Slave bus where read/write operations
can be performed on Slave RAM and Lexichip. The Lexichip Writeable
Control Store (WCS) contains program memory and registers. It can be
accessed via its on-chip Z80 interface which connects directly to the Slave
Bus.
During normal operation, sampled audio is converted into digital data by the
converter circuitry. Digital effects processing is performed by the Lexichip
under the control of both Master and Slave Z80 processors. The M aster Z80,
which handles all operator I/O and housekeeping functions, is able to pass
on DSP control information to the other two processors .The Slave Z80 is
dedicated to the task of controlling the Lexichip and is, therefore, used to
perform any DSP control functions which require precise timing, such as pitch
shifting.
The LXP-5 utilizes two 4 MHz Z80 microprocessors (U4 and 14) in a master/
slave configuration. Tasks are shared between these two processors as
described below :
The Master Z80 (U4) handles basic housekeeping and user interface I/O op¬
erations. It has the ability to write program code and data directly into the
Slave Z80 Program RAM and Lexichip Writeable Control Store (WCS) by
directly accessing the Slave Z80 bus via the Master / Slave Interface. Its
specific tasks are:
• Processing data and instructions to and from the UART
• Processing data and instructions to and from the Lexichip
• Handling user-data input and LED operations
• Maintenence of non-volatile, user-controlled registers.
• Loading and manipulation of Slave processor program code and data
• Controlling Slave processor reset and interrupt functions
• Controlling audio muting hardware
Overview
Z80 Microprocessor
Circuitry
Master Processor Functions

Lexicon LXP-5 Specifications

General

Brand	Lexicon
Model	LXP-5
Category	Recording Equipment
Language	English