Lexicon LXP-5 Service Manual

LXP-5 Service Manual
Circuit
Description
[L] = active Low
[H] = active High
ROM/ U11 Pin 12 [L]
Master ROM enable. Activates the ROM !C, U10.
RAM/ U11 Pin 13 [L]
Master RAM enable. Activates RAM 1C U17.
MSREQ/ U11 Pin 14 [L]
Requests access to Slave bus.
101/ U11 Pin 16 [L]
Enables input buffer so that status of SW2 and 3 can be read.
UART/ U11 Pin 15 [L]
Enables UART 1C for R/W operations.
102/ U11 Pin 17 [L]
Enables input buffer so that status of SW5, LEARN button, Footswitch and
SINT/ can be read.
103 U11 Pin 19 [Hj
Sets slave interupt (SINT/). This output remains high once set by MasterZ80.
SINT/, the active low Slave interrupt signal is produced by inverting 103 with
inverter U1. When Slave Z80 services the interrupt, INTACK/ is generated by
its decoding PAL to clear SI NT/ and gate U18 pin 8 with a signal fed back into
the Master PAL creating an SR latch function set by the Master Z80 and
cleared by the Slave Z80.
104 U11 Pin 18 [H]
Data bits 0,1, and 2 are used to control the following functions :
Bit Ois ANDedwith 104 to produce MSYNC. This syncronizesthe MasterZ80
with the WC signal produced by the Digital Audio Processor by placing Z80
into a wait condition until the falling edge of WC/ occurs.
Bits 1,2,3 and 4 are latched into U5 , a 74HCT174. Bit 1 sets the active low
MUTE/ signal which controls the Audio Muting Circuitry. Bit 2 sets the active
low SRST/ signal which controls Slave Z80 Reset. Bits 3 and 4 control the
status of the multicolor LEARN LED as described previously. Note that the
74HCT174, U5 .outputs are all set low on power up by ZRST/, activating both
MUTE/ and SRST/ and setting the LEARN LED to an OFF condition.
INTACK/ U6 Pin 12 [L]
Slave Interrupt is used to clear the SINT/ signal asserted by the Master Z80.
This signal is created by ANDing the Slave 10RQ and Slave Ml signals. This
is performed by the Z80 to indicate interrupt acknowledgement.
LEX/ U6 Pin 18 [L]
Lexichip Z80 port enable. Allows Z80 R/W access to the internal Writeable
Control Store of the Lexichip.
Signal and Bus
Descriptions
Master PAL
Slave PAL
3-19

Lexicon LXP-5 Specifications

General

Brand	Lexicon
Model	LXP-5
Category	Recording Equipment
Language	English