Roland MSQ-700 Service Notes page 8

MSQ-700
SEP., 1984
IC2 TR2 IC15 FREQ.
H OFF 1.3kHz
L ON 2.1kHz
During the leader period 1.3kHz is generated.
Memory
RAMs 6264 IC8-IC11
MAIN BOARD
The total memory capacity of these RAMs add
up to 32k bytes that are used for storing
note data. These memories are divided into
128 blocks by 256 bytes. Of 128 blocks, one
block is reserved for cordinating RAM memory
itself and for storing CHAIN PLAY data.
Consequently, memories can be used for tone
data are: 32778 -256 = 32512 bytes.
As mentioned ealier, one note (ON/OFF) needs
5 bytes ( 2 bytes for time, 2 for Key events
and 1 for Velocity). Thus, 32512/5 (byte) t
6,500 is the maximum tone number under ideal
conditions -- BENDER or After Toutch can be
memorized with sacrification of tone data in
MIDI mode.
MEMORY BLOCK-
As explained above,one memory block consists
of 256 bytes, this is a minimum unit which
can be handled in storing and reading in the
MSQ-700.This conception should be remembered
when plural track loading is intended.
Data slightly exceeding 256 bytes requires
complete 2 blocks.
BATTERY BACK-UP
BACK UP switch on the rear panel is turned
OFF at the factory for a long battery life.
RAM intitialization is made upon turning ON
of the power with PROTECT OFF, and the RAM
control table is written into the RAM by
the CPU. Necessary information on Initia¬
lization, Protect and Error is found on the
MSQ-700 Owner's Manual.
CMT
OUTPUT TO TAPE (SAVE)
During the leader period 1kHz signal is
placed from PBO and PB1 of IC2. When in
data saving, IC4 counter 1 generates 250us
rectangular which is applied to the CPU via
INT terminals. The Master CPU uses this INT
as a time reference in producing data codes.
For each data 1 or 0, the CPU selects one
of two codes to have l's and 0's distin¬
guishable when they are interleaved with
the same bits and are converted to analog
signals.
INPUT FROM TAPE (LOAD)
Data from the tape is first smoothed and
shaped up by IC12 and fed to IC29 INTERRUPT
SELECTOR which connects the data to DCDA of
IC3 when MODE is placed at TAPE. The serial
data is fed in the form of INT chain to the
master CPU where the data is converted into
parallel format and stored into RAM memories
VERIFY
Data from the tape are fed to the master CPU
just the same as in TAPE LOAD mode except
that data are compared with RAM stored data
for verification.
METRONOME
Control of metronome is done by the Slave
CPU IC5 on the Panel board. There are two
metronome modes according to the setting of
METRONOME on the panel.
LOAD OR PLAY MODE
IC5 sounds metronome upon receiving "RUN"
information from the Master CPU on the Main
Board.
ON MODE
IC5 constantly drives the metronome circuit.
In either mode IC5 outputs metronome drive
pulse from P22 at an 8th note rate in syn¬
chronous with T1 coming from PCO of IC2 on
the Main board.
PITCH CONTROL
IC5 can provide two different click-pitch
patterns: one for PLAY or LOAD, and one for
ON. This is done by varying capacitance
value at pin 2 of IC1 with P20 and/or P21
outputs.
STOP MODE LOAD/PLAY MO
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As can be seen from the timing chart below,
IC5 also outputs data for IC4- lOOus-width
pulse at every 1.6ms. To prevent metronome
signals from entering IC4, IC5 turns PROG
low only for lOOus at 1.6ms intervals.
On the contrary, these lOOus pulses are
filtered out before reaching metronome
circuitry.
JC. J<_ -2L
8