LAN91C100-FD SMSC [SMSC Corporation], LAN91C100-FD Datasheet - Page 49

• Manufacturer Part Number: LAN91C100-FD
• Description: FEAST FAST ETHERNET CONTROLLER WITH FULL DUPLEX CAPABILITY
• Manufacturer: SMSC [SMSC Corporation]

5.5
SMSC DS – LAN91C100FD Rev. D
FEAST Fast Ethernet Controller with Full Duplex Capability
Memory Partitioning
Unlike other controllers, the LAN91C100FD does not require a fixed memory partitioning between transmit
and receive resources. The MMU allocates and de-allocates memory upon different events. An additional
mechanism allows the CPU to prevent the receive process from starving the transmit memory allocation.
Choose Bank Select
Call ALLOCATE
Exit Driver Send
DRIVER SEND
Register 2
Figure 5.7 - Drive Send and Allocate Routines
Write Address Pointer Register
Return Buffers to Upper Layer
Copy Part of TX Data Packet
Set "Ready for Packet" Flag
Write Allocated Packet into
Write Source Address into
Copy Remaining TX Data
Read Allocation Result
Packet # Register
Enqueue Packet
Proper Location
Packet into RAM
PRELIMINARY
into RAM
Register
Yes
Page 49
Read Interrupt Status Register
Issue "Allocate Memory"
Command to MMU
ALLOCATE
Allocation
Passed?
Return
Clear "Ready for Packet" Flag
No
Enable Allocation Interrupt
Store Data Buffer Pointer
Rev. 10/14/2002