Commodore 128 Programmer's Reference Manual page 568

558 COMMODORE 128
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outputs from the VIC chip, as well as an edge-triggered light pen input latch going to <J
the VIC chip.
The output from the SID chip sound generator is buffered and applied directly to j j
an external amplifier, like that found in an external monitor, or modulated and repro- \j
duced in the user's television set. The SID chip also has an external input for mixing
another sound source. \ j
The 8563 video control chip fetches screen data from a dedicated section of RAM j j
referred to as the display RAM and creates an RGBI (Red-Green-Blue-Intensity) output °
for use with an external 80-column monitor. The 8563 also creates all needed signals for
dynamic refresh of its dedicated display RAM. The C128 provides RGBI and composite j j
monochrome outputs from the 8563 chip. O
The cassette port is implemented using the zero page ports available on the 8502
and software control of hardware handshaking. The Commodore serial bus port is imple- j j
mented in a similar manner using a 6526 CIA for I/O. The serial bus works with )J
Commodore serial components, and in C64 mode is actually driven by the software
routines contained in the C64. The User Port is a multipurpose port comprising several
parallel port lines that support peripherals such as slow RS232, modem, etc. The
joystick ports are identical to those on the C64 and are implemented using a 6526 CIA U
to read/write the port.
The video connector has composite video as well as separate chroma and lumi- j j
nance outputs for use with monitors. The 1701 and 1702 Commodore monitors interface JJ
directly to this connector. The RF output jack supplies an RF signal compatible with the
regulations for TV interface devices and is switch selectable between channels 3 and 4. .- ,
Both NTSC and PAL television standards are supported. The RGBI connector and JJ
signal are similar to the ones used by IBM, and are compatible with most monitors
supporting Type I RGBI. Additionally, a composite monochrome signal is available on
the RGBI connector and is generally compatible with NTSC (or PAL) composite. Audio j
is available only from the 40-column video/audio connector. U
SYSTEM SPECIFICATION LJ
This section discusses various features and constraints of the C128 system. Included are {
descriptions of the system and its configurations and limiting factors such as power, ^
loading and environment.
Figure 16-1 shows the C128 system.
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