LAN91C111 Datasheet, PDF (56/125 Pages) SMSC Corporation – 10/100 Non-PCI Ethernet Single Chip MAC + PHY

LAN91C111
8.19 Bank 2 - Pointer Register
OFFSET
6
NAME
POINTER REGISTER
TYPE
READ/WRITE
NOT EMPTY IS
A READ ONLY
BIT
SYMBOL
PTR
HIGH
BYTE
LOW
BYTE
RCV
0
0
AUTO
INCR.
0
0
READ
0
Reserved
NOT
EMPTY
0
0
POINTER LOW
0
0
0
POINTER HIGH
0
0
0
0
0
0
POINTER REGISTER - The value of this register determines the address to be accessed within the transmit or receive
areas. It will auto-increment on accesses to the data register when AUTO INCR. is set. The increment is by one for every
byte access, by two for every word access, and by four for every double word access. When RCV is set the address
refers to the receive area and uses the output of RX FIFO as the packet number, when RCV is clear the address refers
to the transmit area and uses the packet number at the Packet Number Register.
READ - Determines the type of access to follow. If the READ bit is high the operation intended is a read. If the READ
bit is low the operation is a write. Loading a new pointer value, with the READ bit high, generates a pre-fetch into the
Data Register for read purposes.
Readback of the pointer will indicate the value of the address last accessed by the CPU (rather than the last pre-
fetched). This allows any interrupt routine that uses the pointer, to save it and restore it without affecting the process
being interrupted. The Pointer Register should not be loaded until the Data Register FIFO is empty. The NOT EMPTY
bit of this register can be read to determine if the FIFO is empty. On reads, if ARDY is not connected to the host, the
Data Register should not be read before 370ns after the pointer was loaded to allow the Data Register FIFO to fill.
If the pointer is loaded using 8 bit writes, the low byte should be loaded first and the high byte last.
Reserved - Must be 0
NOT EMPTY - When set indicates that the Write Data FIFO is not empty yet. The CPU can verify that the FIFO is empty
before loading a new pointer value. This is a read only bit.
Note: If AUTO INCR. is not set, the pointer must be loaded with a dword aligned value.
DS00002276A-page 56
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