COM20020ILJP Datasheet, PDF (36/72 Pages) Microchip Technology – 5Mbps ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip RAM

5Mbps ARCNET (ANSI 878.1) Controller with 2K x 8 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 6.10 - Setup 1 Register
SYMBOL
P1MODE
FOUR
NACKS
RCVALL
CKP3,2,1
SLOWARB
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 COM20020ID. This bit, when reset, will set the
EXNACK bit after 128 NACKs to Free Buffer Enquiry. The default
is 128.
Do not set.
This bit, when set, allows the COM20020ID 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 COM20020ID's
programmed node ID. This feature can be used to put the
COM20020ID in a 'listen-only' mode, where the transmitter is
disabled and the COM20020ID is not passing tokens. Defaults
low.
These bits are used to determine the data rate of the
COM20020ID. The following table is for a 20 MHz crystal: (Clock
Multiplier is bypassed)
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 COM20020ID 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 12-05-06
Page 36
DATASHEET
SMSC COM20020I Rev D