SMC Networks SMC91C95 - Manual (Page 58)

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I/O SPACE - BANK2
OFFSET NAME TYPE SYMBOL
2 PACKET NUMBER REGISTER READ/WRITE PNR
PACKET NUMBER AT TX AREA
0 0 0 0 0 0 0 0
PACKET NUMBER AT TX AREA - The value
written into this register determines which packet
number is accessible through the TX area. Some
MMU commands use the number stored in this register as the packet number parameter. This
register is cleared by a RESET or a RESET MMU
Command.
OFFSET NAME TYPE SYMBOL
3 ALLOCATION RESULT REGISTER READ ONLY ARR
This register is updated upon an ALLOCATE MEMORY MMU command.
FAILED ALLOCATED PACKET NUMBER
1 0 0 0 0 0 0 0
FAILED - A zero indicates a successful allocation
completion. If the allocation fails the bit is set and
only cleared when the pending allocation is
satisfied. Defaults high upon reset and reset MMU
command. For polling purposes, the ALLOC_INT
in the Interrupt Status Register should be used
because it is synchronized to the read operation.
Sequence:
1) Allocate Command
2) Poll ALLOC_INT bit until set
3) Read Allocation Result Register
ALLOCATED PACKET NUMBER - Packet
number associated with the last memory allocation
request. The value is only valid if the FAILED bit is
clear.
NOTE: For software compatibility with future
versions, the value read from the ARR after an
allocation request is intended to be written into the
PNR as is, without masking higher bits (provided
FAILED = 0).