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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Exponentiation
Acceleration Unit
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
918
Order Number: 306262-004US
25.4.4
EAU Interrupt Register
25.4.5
EAU RAM Registers
The 2-Kbyte EAU RAM can be read and written with certain restrictions. While the EAU
is active, all requests for reads and writes to the RAM will be ignored. The RAM will not
be reset after a power-on or pin reset assertion. The content of the RAM is
indeterminate until they are initialized by the CPU / Intel XScale processor.
Writes to the RAM are all 32-bit, and are triggered by a half-word write to a RAM
address that is the high half of the word. The required usage model is to write a 4-byte
word two bytes at a time from least significant half-word to most significant half-word.
In actual implementation, the register interface stores the bottom two bytes in a write
buffer until the two high bytes are written. Repeated high half-word writes (at other
addresses) will initialize other 32-bit words with half of the writes required to initialize
all bytes individually. Do not attempt to write a byte to the RAM: byte writes trigger a
pre-read operation, as described below, and the data in the write buffer is ignored.
Reads to the RAM are also buffered and accessed with different timing than reads to
registers. Reading values from the EAU takes several cycles, and during this time the
Intel XScale processor is held off. using EAU_DONE. The EAU RAM resides at memory
Table 290, “EAU RAM Memory Locations” on page 919
Register
EAU Count Register
Bits
Name
Description
Reset
Value
Access
31:0
COUNT
Contains the previous value of [COUNT (prior to the start of the last
EAU operation) + the number of EAU cycles for the last EAU
operation]. This register is cleared automatically when a new
command is started.
0x00
RO
Register Name:
EAUINT
Block
Base Address:
0x7000
Offset Address
_200C
Reset Value
0x0000_0000
Register Description:
The EAU Interrupt Register is a single bit used to read and clear
the EAU interrupt.
Access:
(See below.)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
(Reserved)
INT
Register
EAU Status Register
Bits
Name
Description
Reset
Value
Access
31:1
6
(Reserved)
0x00
15:1
(Reserved)
0x00
0
INT
EAU InterruptBit
0: EAU Interrupt is currently inactive
1: EAU Interrupt is currently active. Write 1 to clear
0x0
RW