Technical Description - Hammond XK-1 Service Manual

11. XK-1 Technical description
1. Switching power supply (JRC AES10-5)
This board commutates the AC power input and supplies +5V
power. This +5V power is used as a MGH-94A's power source.
2. Main, CPU, VASE, DSP and JACK on the board MGH-94A
2 CPUs, 2 VASE3s (sound generator), DSP, D/A converter and
jacks are all built in the MGH-94A. The Main CPU and the VASE 3
simulate the tone wheel generator and the multi-contact keying to
provide the effects.
2-1.Main CPU
The U1 means the Main CPU (SH7144). This CPU communicates to
the switch scan, each switch's operation, the LCD display, the
analog-digital conversion for drawbars and volume, the VASE3, the
DSP control and the SUB CPU.
2-2. SUB CPU
The U41 means the SUB CPU (3024). This CPU does key-scan and
communicates with the Main CPU.
2-3. Main memory
Main soft wear is stored at the 16bit flash memory of the U14
(29LV160CBTC). The U15 and U44, 1Mbit SRAM is supplied VCC by
a battery and saves the each parameter. It is also used for a
workspace.
2-4. System reset
The U11 constantly monitors +3.3V and tells the Main CPU to reset
when the voltage is reduced. This circuit helps to switch the back
up SRAM power to the battery(BT1) at the same time.
2-5. VASE3 sound generator
The U29 and 30 is a sound generator LSI and each one has 64
simultaneous tones (Total is 128 tones). 96 out of 128 tones are