82C836 Datasheet, PDF (25/205 Pages) List of Unclassifed Manufacturers – Single-Chip 386sx AT

s Signal Descriptions
Pin Assignments
Table 2-5. I/O Channel Interface Signals (continued)
Pin
Type
96
Input
89
Output
47
Output
45
Output
43
Output
91
Output
93
Output
95
Output
55
Output
Name
DRQ7/-CAS1H
-DACK0/-DACKEN
-DACK1/DACKA
-DACK2/DACKB
-DACK3/DACKC
-DACK5/-CAS3L
-DACK6/-CAS2L
-DACK7/-CAS1L
TC
Description
DMA Request 0-3, 5-7 are asynchronous requests used by
peripherals to request DMA services. These requests are
prioritized with DRQ0 having the highest priority and
DRQ7 the lowest. DRQ must be held active until the
corresponding DMA acknowledge (DACK) line goes
active. In MRA mode, the functions of these pins change
as indicated.
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DMA Acknowledge 0-3, 5-7 are active-low acknowledge
signals issued by the 82C836 after a DMA service request
(via a DRQ line) and successful arbitration. During
power-on reset, these signals are used for Reset Strap
options. In MRA mode, the functions of these pins change
as indicated.
Terminal Count is an active-high output pulse to the I/O
channel that indicates the end of a DMA transfer.
Table 2-6. Miscellaneous Signals
Pin
Type
39
Input
Name
PWRGOOD
138 Output
CPURST
134 Output
XRST
132 Output
SPKOUT
Description
Power Good is an active-high input from the power supply.
When this signal is high, it indicates all power supply
voltages have reached their working levels. CPURST
(pin 138) and XRST (pin 134) remain high for at least
200µs after PWRGOOD goes high.
CPU Reset is an active-high output that resets the 80386sx
processor. CPURST goes active at power-up or during a
software-initiated CPU reset. CPURST without XRST is
often used to return the CPU to real mode from protected
mode.
Peripheral Reset is an active-high output that resets external
peripherals and the coprocessor (if present) during
power-up.
Speaker data is a waveform (the output of channel 2 of the
timer/counter gated by bit 1 of port 61H) that is routed to
an external driver circuit, a low pass filter, and then to the
speaker.
2-8 Revision 3.0
PRELIMINARY
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