W89C840F
28:21
R/W
REIT
Receive Early Interrupt Threshold
Dur i ng r ecei vi ng packet , W89C840F will assert an i nt er r upt
r equest when t he byt e number of the received data, which the
receive DMA has moved them into the data buffer, excesses the
receive early interrupt threshold.
To set this field 00H will disable receive early interrupt function.
The setting of the receive early interrupt is as following.
REIT[28:21] receive early interrupt threshold
----------------
-----------------
4 bytes
01H
02H
--
8 bytes
--
0fH
10H
--
60 bytes
64 bytes
--
ffH
020 bytes
20:14
R/W
TTH
Transmit Threshold.
These bits select the transmit threshold level of the transmit FIFO.
The packets t r ansmi t st ar t immediately once the data queued
into the transmit FIFO has reached the threshold level. The
t r ansmi ssi on i s also started immediately when the full packet
has been transferred into the transmit FIFO even though the frame
length is less than the TTH level.
To change this bit, the transmit state machine must be in Idle state.
The following table shows there is a difference with 16 bytes for
each consecutive setting value in this field, except that the first one
in the table.
TTH[20:14]
---------------
-----------------
full packet
16 bytes
32 bytes
--
00H
01H
02H
--
0fH
10H
--
240 bytes
256 bytes
--
7fH
2032 bytes
- 42 -
ETC [ ETC ]
