Enter Packet Transmit Process
Exit: can’t issue command
Note: Issuing a command
at this point will cause
previous transmit frame
to be lost.
Is
TxCMD
Yes pending?
No
Host Writes Transmit Command
to the TxCMD Register
CS8920A
Host Writes Transmit Frame
Length to the TxLength Register
Transmit Request
Host Reads the BusST
Register (Register 18)
Host Enters Interrupt Routine
Host Reads
ISQ
Rdy4
TxNOW
Yes
bit = 1?
No
Exit WAIT-for-interrupt
No Rdy4Tx Yes
bit = 1?
Wait for next Interrupt
CS8920A Commits
Buffer Space to
Transmit Frame
Host Writes
Transmit Frame
to CS8920A
CS8920A
Transmits Frame
Exit Transmit Process
Figure 5.13. Transmit Operation in Interrupt Mode
112
DS238PP2