Memory
The 130XE operating system is resident to 16k X 8 ROM. The ROM input CPU address lines
A0 through A13 and the chip selects from the MMU, generates data on CPU data lines D0
through D7. RAM is organized as 16 X 64k x 1 or 4 X 64k X 4 chips, two for each data line.
48K RAM is directly available, but more is accessible under DOS 2.5.
Memory Management Unit (MMU)
The Memory Management (Address Decoding) circuitry consists of a Programmable Array
Logic (PAL) and one 3 to 8 decoder. The input to this circuitry are the address lines A8 thru
A15 and control signals like ROM enable (from PIA) and Refresh. The outputs of this
circuitry are GTIA chip select (D0XX), Expansion selects (D1XX), POKEY chip select
(D2XX), PIA chip select (D3XX), Cartridge selects (D5XX), O.S. ROM selects and RAM
selects.
The RF Modulator
The RF Modulator inputs the composite video from the video summation circuitry and the
monoaural audio signals and produces a modulated signal suitable for the television.
The modulated signal will have the following characteristics with a 75Ω termination:
Maximum Voltage: 2 mV
Minimum Voltage: 1 mV
Audio Sound Carrier Frequency: 5.5 MHz
Frequency Response:
Ch. 3 61.25 MHz ± 0.5
Ch. 2 55.25 MHz
Power Supply
The 130XE has a external power supply. The power supply jack, power on switch and filters
are resident on the motherboard. The power supply accepts a 5V DC input through the power
jack. An external step-down transformer accepts 115V AC or 230V AC from the power line
and steps it down to 9VAC. The 9VAC input is rectified by a bridge rectifier and then
regulated power output from the regulator.
130XE Personal Computer
Field Service Manual 1-9
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