82596CA Datasheet, PDF (24/76 Pages) Intel Corporation – HIGH-PERFORMANCE 32-BIT LOCAL AREA NETWORK COPROCESSOR

82596CA
CONTROLLING THE 82596CA
The host CPU controls the 82596 with the commands data structures and methods described in this section
The CPU and the 82596 communicate through shared memory structures The 82596 contains two indepen-
dent units the Command Unit and the Receive Unit The Command Unit executes commands from the CPU
and the Receive Unit handles frame reception These two units are controlled and monitored by the CPU
through a shared memory structure called the System Control Block (SCB) The CPU and the 82596 use the
CA and INT signals to communicate with the SCB
82596 CPU ACCESS INTERFACE (PORT)
The 82596 has a CPU access interface that allows the host CPU to do four things
 Write an alternative System Configuration Pointer address
 Write an alternative Dump area pointer and perform Dump
 Execute a software reset
 Execute a self-test
The following events initiate the CPU access state
 Presence of an address on the D₃₁ – D₄ data bus pins
 The D₃ – D₀ pins are used to select one of the four functions
 The PORT input pin is asserted as in a regular write cycle
NOTE
The SCP Dump and Self-Test addresses must be 16-byte aligned
The 82596 requires two 16-bit write cycles for a port command The first write holds the internal machines and
reads the first 16 bits the second activates the PORT command and reads the second 16 bits
The PORT Reset is useful when only the 82596 needs to be reset The CPU must wait for 10-system and 5-se-
rial clocks before issuing another CA to the 82596 this new CA begins a new initialization process
The Dump function is useful for troubleshooting No Response problems If the chip is in a No Response state
the PORT Dump operation can be executed and a PORT Reset can be used to reinitialize the 82596 without
disturbing the rest of the system
The Self-Test function can be used for board testing the 82596 will execute a self-test and write the results to
memory
Function
Reset
Self-Test
SCP
Dump
Table 2 PORT Function Selection
D31
D4
D0
Addresses and Results
D3
D2
D1
D0
A31
Don’t Care
A4
0
0
0
0
A31
Self-Test Results Address
A4
0
0
0
1
A31
Alternative SCP Address
A4
0
0
1
0
A31
Dump Area Pointer
A4
0
0
1
1
MEMORY ADDRESSING FORMATS
The 82596 accesses memory by 32-bit addresses There are two types of 32-bit addresses linear and seg-
mented The type of address used depends on the 82596 operating mode and the type of memory structure it
is addressing The 82596 has three operating modes
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