vt82c42 ETC-unknow, vt82c42 Datasheet - Page 9

• Manufacturer Part Number: vt82c42
• Description: Vt82c42 Keyboard Controller
• Manufacturer: ETC-unknow

P16,P17 are input only pins. They have a 50K ohm pull up internally.
P20-P26 are all output only pins, each has 4mA TTL-compatible output. P27 is also output only pin, but with
16mA TTL-compatible output.
For two-way port pins, P
sustained tri-state output. That means when it is to be floated high, it will be driven high for one 8Mhz cycle
before goes to float. The external connection is suggested to have a 4.7K pull-up resistor to maintain high after
floating. The following logic diagram shows the corresponding functions. Note that the part surrounded by
dash lines is a bi-directional TTL-compatible output with 4mA driving capabilities.
TH_SS, TH_PROG and TH_SSPP are all input pins, and must be tied to high for normal operation. TL_EA is
an input pin, and must be tied to low for normal operation.
SYNC is output pin, which drives some internal states out, this pin is only useful when in debugging stage. For
normal operation, it should leave opened.
MSLKMD is the mouse lock enable pin. When this pin is tied low, the Mouse Lock mode is enabled,
otherwise the Mouse Lock mode is disabled.
XTAL1, XTAL2 is the clocking source input of VT82C42, it can be implemented as in the figure 5. or figure
6. underneath:
VIA Technologies, Inc.
Figure 5. Crystal Connections for Clock source for VT82C42
10
-P
P10O
CLOCK
15
, when floated (by written "1" to the port), the signals from these pins are all
20pf
20pf
P10I
Fig 4.
1 - 12 MHz
-7-
50K ohm
VCC
XTAL1
XTAL2
P10
VT82C42