CS8900A
Crystal LAN™ ISA Ethernet Controller
Enter Packet Transmit Process
Is
TxCMD
pending?
Exit: can’t Issue command
Yes
Note: Issuing a command
at this point will cause
previous transmit frame
to be lost.
No
Host Writes Transmit Command
to the TxCMD Register
Host Writes Transmit Frame
Length to the TxLength Register
Transmit Request
Host Reads the BusST
Register (Register 18)
Rdy4
Yes
TxNOW
bit = 1?
No
Exit WAIT-for-interrupt
Host Enters Interrupt Routine
Host Reads
ISQ
CS8900A Commits
Buffer Space to
Transmit Frame
No
Yes
Rdy4Tx
bit = 1?
Host Writes
Transmit Frame
to CS8900A
Process other events
that caused interrupt
CS8900A
Transmits Frame
Exit Transmit Process
Figure 31. Transmit Operation in Interrupt Mode
any yet-to-be-transmitted frames queued in the
on-chip memory, are cleared and not transmit-
ted. The host should make TxLength = 0 when
using the Force bit.
3) There is a transmit under-run, and the Tx-
Underrun bit (Register C, BufEvent, Bit 9) is
set.
Successful transmission is indicated when the
TxOK bit (Register 8, TxEvent, Bit 8) is set.
Or:
CIRRUS LOGIC PRODUCT DATA SHEET
104
DS271PP3
CIRRUS [ CIRRUS LOGIC ]
