COM20051I Datasheet, PDF (53/74 Pages) SMSC Corporation – Integrated Microcontroller and ARCNET (ANSI 878.1) Interface

Initiating Transmissions
The Transmit Service routine can only execute after a transmission occurs. Therefore, initial transmit commands
must originate from routines external to the Transmit Interrupt service routine. The Transmit ISR can only
transmit packets if and only if packets are pending transmission upon entry into the routine. Normally this is not the
case, thus the programmer must take care to monitor and update the TX_PEND_REG for each transmission.
BIT 7
NOT
USED
BIT 6
BIT 5
TX CMD #2 TX CMD #1
ISSUED ISSUED
TX_PEND_REG
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
NOT
USED
TX PEND. TX PEND. TX PEND. TX PEND.
IN
IN
IN
IN
BUFFER 4 BUFFER 3 BUFFER 2 BUFFER 1
BIT 7
BIT 6
BIT 5
RAM_BUF_REG
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
NOT
USED
NOT
USED
NOT
USED
NOT
USED
NOT
USED
NOT
USED
RX BUF RX BUF
2
1
BIT 7
BIT 6
BIT 5
RX_PAGE_REG
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RECEIVE COMMAND PAGE #2
RECEIVE COMMAND PAGE #1
SMSC DS – COM20051I
Page 53
Rev. 03/27/2000