91C100FDREVB datasheet(27/68 Pages) SMSC

27 / 68 page

SMSC DS – LAN91C100FD REV. B

Page 27

Rev. 05/31/2000

BANK 1

OFFSET

NAME

TYPE

SYMBOL

CONTROL REGISTER

READ/WRITE

CTR

HIGH

BYTE

RCV_

BAD

AUTO

RELEAS

LOW

BYTE

ENABLE

EEPROM

SELECT

RELOAD

STORE

RCV_BAD - When set, bad CRC packets are received. When clear bad CRC packets do not generate interrupts and their

memory is released. Note: nRXDISC, when asserted, overrides RCV_BAD. Also, RCV_ BAD does not modify the function

of RCV DISCARD in the early receive register.

AUTO RELEASE - When set, transmit pages are released by transmit completion if the transmission was successful (when

TX_SUC is set). In that case there is no status word associated with its packet number, and successful packet numbers are

not even written into the TX COMPLETION FIFO. A sequence of transmit packets will generate an interrupt only when the

sequence is completely transmitted (TX EMPTY INT will be set), or when a packet in the sequence experiences a fatal

error (TX INT will be set). Upon a fatal error TXENA is cleared and the transmission sequence stops. The packet number

that failed, is present in the FIFO PORTS register, and its pages are not released, allowing the CPU to restart the

sequence after corrective action is taken.

LE ENABLE - Link Error Enable. When set it enables the LINK_OK bit transition as one of the interrupts merged into the

EPH INT bit. Clearing the LE ENABLE bit after an EPH INT interrupt, caused by a LINK_OK transition, will acknowledge

the interrupt. LE ENABLE defaults low (disabled).

CR ENABLE - Counter Roll over Enable. When set, it enables the CTR_ROL bit as one of the interrupts merged into the

EPH INT bit. Reading the COUNTER register after an EPH INT interrupt caused by a counter rollover, will acknowledge the

interrupt. CR ENABLE defaults low (disabled).

TE ENABLE - Transmit Error Enable. When set it enables Transmit Error as one of the interrupts merged into the EPH INT

bit. An EPH INT interrupt caused by a transmitter error is acknowledged by setting TXENA bit in the TCR register to 1 or by

clearing the TE ENABLE bit. TE ENABLE defaults low (disabled). Transmit Error is any condition that clears TXENA with

TX_SUC staying low as described in the EPHSR register.

EEPROM SELECT - This bit allows the CPU to specify which registers the EEPROM RELOAD or STORE refers to. When

high, the General Purpose Register is the only register read or written. When low, RELOAD reads Configuration, Base and

Individual Address, and STORE writes the Configuration and Base registers.

RELOAD - When set it will read the EEPROM and update relevant registers with its contents. Clears upon completing the

operation.

STORE - When set, stores the contents of all relevant registers in the serial EEPROM. Clears upon completing the

operation.

Note: When an EEPROM access is in progress the STORE and RELOAD bits will be read back as high. The remaining 14

bits of this register will be invalid. During this time attempted read/write operations, other than polling the EEPROM status,

will NOT have any effect on the internal registers. The CPU can resume accesses to the LAN91C100FD after both bits are

low. A worst case RELOAD operation initiated by RESET or by software takes less than 750

µs.

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