91C100FDREVB Datasheet, PDF (23/68 Pages) SMSC Corporation – FEAST FAST ETHERNET CONTROLLER WITH FULL DUPLEX CAPABILITY

BANK 0
OFFSET
6
NAME
COUNTER REGISTER
TYPE
READ ONLY
SYMBOL
ECR
Counts four parameters for MAC statistics. When any counter reaches 15 an interrupt is issued. All counters are cleared
when reading the register and do not wrap around beyond 15.
HIGH
BYTE
LOW
BYTE
NUMBER OF EXC. DEFFERED TX
0
0
0
0
MULTIPLE COLLISION COUNT
0
0
0
0
NUMBER OF DEFFERED TX
0
0
0
0
SINGLE COLLISION COUNT
0
0
0
0
Each four bit counter is incremented every time the corresponding event, as defined in the EPH STATUS REGISTER bit
description, occurs. Note that the counters can only increment once per enqueued transmit packet, never faster, limiting the
rate of interrupts that can be generated by the counters. For example if a packet is successfully transmitted after one
collision the SINGLE COLLISION COUNT field is incremented by one. If a packet experiences between 2 to 16 collisions,
the MULTIPLE COLLISION COUNT field is incremented by one. If a packet experiences deferral the NUMBER OF
DEFERRED TX field is incremented by one, even if the packet experienced multiple deferrals during its collision retries.
The COUNTER REGISTER facilitates maintaining statistics in the AUTO RELEASE mode where no transmit interrupts are
generated on successful transmissions.
Reading the register in the transmit service routine will be enough to maintain statistics.
BANK 0
OFFSET
8
NAME
MEMORY INFORMATION REGISTER
TYPE
READ ONLY
SYMBOL
MIR
HIGH
BYTE
FREE MEMORY AVAILABLE (IN BYTES * 256 * M)
1
1
1
1
1
1
1
1
LOW
BYTE
MEMORY SIZE (IN BYTES *256 * M)
1
1
1
1
1
1
1
1
FREE MEMORY AVAILABLE - This register can be read at any time to determine the amount of free memory. The register
defaults to the MEMORY SIZE upon reset or upon the RESET MMU command.
MEMORY SIZE - This register can be read to determine the total memory size.
All memory related information is represented in 256 * M byte units, where the multiplier M is determined by the MCR upper
byte.
These register default to FFh, which should be interpreted as 256.
SMSC DS – LAN91C100FD REV. B
Page 23
Rev. 05/31/2000