Commodore 128 Programmer's Reference Manual page 600

590 COMMODORE 128
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■ Ao-A6: Multiplexed address lines, pins 32 through 38. During row address L
time, Ao-A8 are driven on Ao-A5. During column address time, A8-Ai3 are
driven on Aq- A5 and A6 is held at 1. During a processor read or write, Aa-A5 i /
serve as address inputs that latch on the low edge or /RAS. jj
■ A-A10: Static address lines, pins 39 through 42. These address lines are used
for non-multiplexed VIC memory accesses, such as to character ROM and ^
color RAM. I I
■ 1MHz: The 1 MHz system clock, pin 18. All system bus activity is referenced <~>
to this clock.
■ 2MHz: This is the changing system clock, which will be either 1 MHz or 2 j j
MHz. If the 2 MHz bit is clear, no VIC or external DMA is taking place, and [J
no I/O operation is occurring, the clock will be 2 MHz; otherwise it will be 1
MHz. Found at pin 23. \
■ Z80 Phi: The special 4 MHz Z80 clock, pin 25. !
■ /IOACC: From PLA, indicating an I/O chip access for clock stretching. Pin 22 ^
of the VIC.
■ /RAS: Row address strobe for DRAMs, pin 19. ) j
■ /CAS: Column address strobe for DRAMs, pin 20. U
■ MUX: Address multiplexing control for DRAMs, pin 21.
■ /IRQ: Interrupt output, used to signal one of the various internal interrupt i /
sources has taken place. Requires a pull-up, found at pin 8 on the chip. [J
■ AEC: Address Enable Control, high for processor enable on the shared bus,
low for VIC cycle and VIC or external DMA. Found at pin 12 of the VIC.
■ BA: Bus Available signal, used to DMA processor. Pin 10. j
■ Ko-K2: Extended keyboard strobe bits, pins 26 to 28. V~J
■ LP: Edge triggered latch for light pen input. Pin 9 of the VIC chip.
\ {
The signals comprised in the video interface, i.e., all the signals required to create \j
a color video image, are:
■ PH IN: The fundamental shift rate clock, also called the dot clock. Used as the M
reference for all system clocks. Located at pin 30.
■ PH CL: The color clock, used to derive the chroma signal. Pin 29.
■ SYNC: Output containing composite sync information, video data and lumi- ) [
nance information. Requires a pull-up, pin 17. O
■ COLOR: Output containing all color-based video information. Open source
output, should be tied through a resistor to ground. Found at pin 16. f /
ELECTRICAL SPECIFICATION °
Tables 16-12 and 16-13 specify the electrical operation of the VIC chip in its new form. }
These specs include absolute maximum ratings and maximum operating conditions. ^