83C795 Datasheet, PDF (21/136 Pages) List of Unclassifed Manufacturers – Ethernet System Controller

83C795
PIN LIST
Mnemonic
RLED
R OMCS
RX+
RX-
S A19 - 14
S A13 - 11
S A10 - 09
S A08 - 06
S A05 - 00
S BHE
S D15 - 14
S D13 - 12
S D11 - 10
S D09 - 08
S D07
S D06 - 04
S D03 - 02
S D01 - 00
S ME MR
S ME MW
T ES TA
TESTB
Pin Number I/O
130
I/O
138
O
124
I
123
88 - 83
I/O
78 - 76
44 - 43
38 - 37
35 - 30
20
I
45 - 46
I/O
48 - 49
51 - 52
54 - 55
69
65 - 63
61 - 60
58 - 57
74
I/O
75
I/O
117
I
118
Description
R E CV LE D DR IVE R . When on, R LE D drives low to turn on an
external LE D. If no data is received, R LE D is off. If data is
received, R LE D goes active for approximately 50ms longer than
the received packet length. T his pin als o s erves as the E E R OM
data in pin (E E DI) and is used as the s can data input (formerly
S CANIN) in s can mode.
BIOS R OM OUT PUT E NABLE . Active low. Chip S elect for R OM
BIOS . Us ed for XT XE in s ome test modes .
AUI R E CE IVE . T he Manches ter encoded data from the external
trans ceiver is received on R X+ / R X-.
PC ADDR E S S BUS . Normal timing vers ion of s ystem addres s
lines. T hes e s ignals are active high.
PC BUS HIGH E NABLE . Active low. Indicates a trans fer of data on
the upper byte of the data bus, S D8 through S D15.
S YS T E M DATA BUS . Data input and output to hos t and shared
memory. T hes e signals are active high.
LOW ME MOR Y R E AD S T R OBE . R eads buffer memory onto the
PC data bus . It is active only when the memory addres s is within
the first 1Mb of memory space. Active low.
LOW ME MOR Y WR IT E S T R OBE . Writes buffer memory from the
PC data bus . S ME MW is active only when the memory address is
within the firs t 1Mb of memory s pace. Active low.
I/O-MAPPING CONTROL PINS. All signal pins on the 83C795
(except for the analog pins) have been divided into two groups,
GROUPA and GROUPB. The functionality of these pins is
controlled by the two test pins, as follows:
TESTA
1
1
0
0
TESTB
1
0
1
0
GROUPA
NORMAL
1
0
TRISTATE
GROUPB
NORMAL
0
1
TRISTATE
TABLE 4-1. 83C795 PIN ASSIGNMENTS (CONT.)
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