Epson PX-8 Technical Manual page 164

REV.-A
3.2 RAM Disk Unit
Two models of 60K and 1 20K bytes are available. The models have the same circuit and operates
exactly the same way. Only the difference is whether 64K or 128K bytes of DRAM are installed.
The RAM disk unit has a Z-80 CPU built in and is operated asynchronously with the Main Frame.
3.2.1 Major Circuit Elements
The RAM disk unit is built on a circuit board which contains casing components and the following
major circuit elements shown and listed below including a battery.
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Fig. 3-29 RAM Disk Board Element Lay-Out
Table 3-2 Major Circuit Element
No. Element Function No. Element
Function
1 Connector CN1
Interface the data and address
2 Battery 4.8V, 480mAH
busses with Main Frame.
3 SW 1
Write protect control
4 SW2
Connect/disconnect the built-in bat-
ON: Protect OFF: Unprotect tery - the line normally connected.
5 Jumper J1
Define RAM capacity (60 K or 120
6 JumperJ2 Z-80 CPU selection.
K).
7 ROM (27C32) Control for RAM disk Operation. 8 D-RAM
64/1 28 K D-RAM
9
Gate array
Control for DRAM read/write. 10
Crystal resona-
Provide a clock signal of 9.8 MHz
(GAH40D)
tor CR1
11
Crystal resona-
Provide a clock signal of 32.768kHz. 12 CPU Z-80
Control the RAM disk unit - oper-
tor (R2)
ates at a clock rate of 2.45 MHz.
3-18