COM20022I-3V Datasheet, PDF (44/83 Pages) SMSC Corporation – 10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM

BIT
BIT NAME
1,0 Reconfiguration
Timer 1, 0
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM
Datasheet
SYMBOL
RCNTM1,
0
DESCRIPTION
These bits are used to program the reconfiguration timer as
a function of maximum node count. These bits set the time
out period of the reconfiguration timer as shown below. The
time out periods shown are for 10 Mbps.
RCNTM1 RCNTM0
Time Out
Period
Max Node Count
0
0
210 mS
Up to 255 nodes
0
1
52.5 mS Up to 64 nodes
1
0
26.25 mS Up to 32 nodes
1
1
13.125 mS* Up to 16 nodes
Note*: The node ID value 255 must exist in the network for
13.125 mS timeout to be valid.
BIT
BIT NAME
7 16 Bit Access
6 Reserved
5 Internal Terminal
Counter Enable;
Re-Trigger mode
4 Terminal Count
Bit 8
Refresh
Synchronous
Gate Time
Table 6.14 - Bus Control Register
SYMBOL
W16
ITCEN/
RTRG
TC8/
RSYN/
GTTM
DESCRIPTION
This bit is used to Disable/Enable the 16 bit access. It
influences both CPU cycle and DMA cycle. W16= 0: Disable
(Default); W16= 1: Enable
This bit is undefined.
The function of this bit is mode dependent. ITCEN is for Non-
Burst or Burst mode. RTRG is for the two Programmable-
Burst modes.
ITCEN = 0: Terminate the DMA only by External TC. ITCEN
= 1: Terminate the DMA by Internal or External TC.
RTRG = 0: External Re-Trigger mode; Negated DREQ pin is
Re-asserted by falling edge of nREFEX pin. RTRG = 1:
Internal Re-Trigger mode; Negated DREQ pin is Re-asserted
by timeout of internal gate timer (350ns/750ns).
The function of this bit is mode dependent. TC8 is for Non-
burst or burst mode. RSYN and GTTM are for the two
Programmable-Burst modes. RSYN is for External Re-
Trigger mode. GTTM is for internal Re-Trigger mode.
Non-burst or burst mode:
TC8: Bit 8 (MSB) of 9 bit Terminal Count setting register.
The other 8 bits are in the DMA Count register. Terminal
Count setting register is ignored when ITCEN = 0.
Programmable-Burst and External Re-Trigger mode:
RSYN = 0: DMA is started Immediately.
RSYN = 1: DMA is started after Refresh execution.
Programmable-Burst and Internal Re-Trigger mode:
GTTM = 0: Gate Time is 350nS (min)
GTTM = 1: Gate Time is 750nS (min)
Revision 02-27-06
Page 44
DATASHEET
SMSC COM20022I 3V