10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM
Datasheet
Chapter 3
PIN NO
44,45,
46
NAME
Description of Pin Functions
SYMBOL
I/O
DESCRIPTION
MICROCONTROLLER INTERFACE
IN
A0/nMUX
On a non-multiplexed mode, A0-A2 are address input bits.
(A0 is the LSB) On a multiplexed address/data bus, nMUX
IN
A1
tied Low, A1 is left open, and ALE is tied to the Address
Latch Enable signal. A1 is connected to an internal pull-up
resistor.
IN
A2/ALE
I/O
AD0-AD2,
On a non-multiplexed bus, these signals are used as the
D3-D7
lower byte data bus lines. On a multiplexed address/data
bus, AD0-AD2 act as the address lines (latched by ALE)
and as the low data lines. D3-D7 are always used for data
only. These signals are connected to internal pull-up
resistors.
D8-D15
I/O
D8-D15 are always used as the higher byte data bus lines
only for 16bit internal RAM access. When the 16bit access
is disabled, these signals are always Hi-Z. Enabling or
disabling the 16bit access is programmable. A data
swapper is built in. These signals are connected to internal
pull-up resistors.
nWR/DIR
IN
nWR is for 80xx CPU, nWR is Write signal input. Active
Low.
DIR is for 68xx CPU, DIR is Bus Direction signal input.
(Low: Write, High: Read.)
nRD/nDS
IN
nRD is for 80xx CPU, nRD is Read signal input. Active Low.
nDS is for 68xx CPU, nDS is Data Strobe signal input.
Active Low.
nRESET
IN
Hardware reset signal. Active Low.
nINTR
OUT
Interrupt signal output. Active Low.
nCS
IN
Chip Select input. Active Low.
nIOCS16
OUT
This signal is an active Low signal which indicates
accessing 16bit data only by CPU. This signal becomes
active when CPU accesses to data register only if W16 bit
is 1. This signal is same as on ISA Bus signal, but it’s not
OPEN-DRAIN. An external OPEN-DRAIN Buffer is needed
when this signal connects to the ISA Bus.
BUSTMG
IN
Read and Write Bus Access Timing mode selecting signal.
Status of this signal effects CPU and DMA Timing.
L: High speed timing mode (only for non-multiplexed bus)
H: Normal timing mode
This signal is connected to internal pull-up registers.
DREQ
OUT
DMA Request signal. Active polarity is programmable.
Default is active high.
nDACK
IN
DMA Acknowledge signal. Active Low. When BUSTMG is
High, this signal is connected to internal pull-up registers
TC
IN
Terminal Count signal. Active polarity is programmable.
Default is active high. When BUSTMG is High, this signal is
connected to the internal pull-up resistor.
nREFEX
IN
Refresh execution signal. Falling edge detection. This
signal is connected to the internal pull-up resistor.
Address 0-2
1,2,4,
7,9,
10,12, 13
Data 0-7
47, 48,
3,5,
14-17
Data 8-15
37
nWrite/
Direction
39
nRead/
nData Strobe
nReset In
nInterrupt
nChip Select
nI/O
16 Bit
Indicator
31
34
36
42
26
Read/Write
Bus Timing
Select
33
35
38
DMA
Request
DMA Ack
Terminal
Count
Refresh
Execution
40
Revision 02-27-06
Page 8
SMSC COM20022I
DATASHEET
SMSC [ SMSC CORPORATION ]
