82C836 Datasheet, PDF (26/205 Pages) List of Unclassifed Manufacturers – Single-Chip 386sx AT

Pin Assignments
Signal Pinouts s
Table 2-6. Miscellaneous Signals (continued)
Pin
Type
Name
Description
141
Bidirectional
MFP5
Multi Function Pin 5 is a bidirectional pin that has two
functions (see -DACK5 in ‘‘Reset Strap Options ’’): In
internal RTC mode, MFP5 is the Power Sense (PS) input,
active high, indicating the state of the battery. The PS
signal should be powered from the battery back-up circuit.
140
Input
126
Input
130
Output
129
Input
125
Input
MFP4
MFP3
MFP2
MFP1
MFP0
In external RTC mode, MFP5 is the Real Time Clock Chip
Select (-RTCCS) active low. It is a decode of the I/O
address range 070H-071H.
Multi Function Pin 4 is an input that has two functions (see
-DACK5 in ‘‘Reset Strap Options ’’). In internal RTC mode,
MFP4 is the 32KHz Oscillator Input, which should be
connected to a square wave source with a frequency of
32.768KHz. This input signal is the timing reference for
the internal RTC of the 82C836. In external RTC mode,
MFP4 is Interrupt Request 8 (IRQ08) from the external
RTC.
Multi Function Pin 3 is an input pin driven by the -RESET2
signal from the 8042 keyboard controller. In response to
this input (active low), the 82C836 generates CPURST to
reset the CPU. The signal is under software control via the
8042. This pin may have an alternate function in a future
version of the 82C836, but only the -RESET2 function is
available at present.
Multi Function Pin 2 is an output pin used for 8042 Chip
Select (-8042CS). This signal, an active-low output to the
8042 keyboard controller, is a decode of the I/O address
range 060H-06FH. This pin may have an alternate function
in a future verison of the 82C836, but only the -8042CS
function is available at present.
Multi Function Pin 1 is an input pin driven by the
GATEA20 signal from the 8042 keyboard controller. In
response to a low level on this pin, the 82C836 keeps
MODA20 low during CPU cycles (depending on Fast
GATEA20, port 92H). A high level on GATEA20 allows
MODA20 to follow A20. This pin may have an alternate
function in a future version of the 82C836, but only the
GATEA20 function is available at present.
Mutli Function Pin 0 is an input pin acting as Interrupt
Request 1 (IRQ1). This signal, an active-high input from
the 8042 keyboard controller, is used by the 82C836’s
internal interrupt controller. This pin may have an alternate
function in a future version of the 82C836, but only the
IRQ1 function is available at present.
Signal Pinouts
The signal pinouts for the 82C836 CHIPSet are summarized in Tables 2-7 and 2-8.
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