COM20022I-3.3V Datasheet, PDF (36/73 Pages) SMSC Corporation – 10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM

10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
BIT
BIT NAME
7 Pulse1 Mode
6 Four NACKS
5 Reserved
4 Receive All
3,2,1 Clock Prescaler
Bits 3,2,1
0 Slow Arbitration
Select
Table 6.12 - Setup 1 Register
SYMBOL
P1MODE
FOUR
NACKS
RCVALL
CKP3,2,1
DESCRIPTION
This bit determines the type of PULSE1 output driver used
in Backplane Mode. When high, a push/pull output is
used. When low, an open drain output is used. The
default is open drain.
This bit, when set, will cause the EXNACK bit in the
Diagnostic Status Register to set after four NACKs to Free
Buffer Enquiry are detected by the COM20022I 3V. This
bit, when reset, will set the EXNACK bit after 128 NACKs
to Free Buffer Enquiry. The default is 128.
Do not set. It must be 0.
This bit, when set, allows the COM20022I 3V to receive all
valid data packets on the network, regardless of their
destination ID. This mode can be used to implement a
network monitor with the transmitter on- or off-line. Note
that ACKs are only sent for packets received with a
destination ID equal to the COM20022I 3V's programmed
node ID. This feature can be used to put the COM20022I
3V in a 'listen-only' mode, where the transmitter is
disabled and the COM20022I 3V is not passing tokens.
Defaults low.
These bits are used to determine the data rate of the
COM20022I 3V. The following table is for a 20 MHz
crystal: (Clock Multiplier is bypassed)
SLOWARB
CKP3 CKP2 CKP1 DIVISOR
SPEED
0
0
0
8
2.5Mbs
0
0
1
16
1.25Mbs
0
1
0
32
625Kbs
0
1
1
64
312.5Kbs
1
0
0
128
156.25Kbs
Note: The lowest data rate achievable by the COM20022I
3V is 156.25Kbs. Defaults to 000 or 2.5Mbs. For
Clock Multiplier output clock speed greater than 20
MHz, CKP3, CKP2 and CKP1 must all be zero.
This bit, when set, will divide the arbitration clock by 2.
Memory cycle times will increase when slow arbitration is
selected.
Note: For clock multiplier output clock speeds greater
than 40 MHz, SLOWARB must be set. Defaults to
low.
Revision 03-08-07
Page 36
DATASHEET
SMSC COM20022I 3.3V Rev.C