82596DX Datasheet, PDF (32/77 Pages) Intel Corporation – HIGH-PERFORMANCE 32-BIT LOCAL AREA NETWORK COPROCESSOR

82596DX SX
31
ACK
ODD WORD
16 15
0 CUC R RUC 0 0 0 0 STAT
EVEN WORD
0 CUS
RUS
COMMAND BLOCK ADDRESS
RECEIVE FRAME AREA ADDRESS
CRC ERRORS
ALIGNMENT ERRORS
RESOURCE ERRORS ( )
OVERRUN ERRORS ( )
RCVCDT ERRORS ( )
SHORT FRAME ERRORS
T-ON TIMER
In MONITOR mode these counters change function
T-OFF TIMER
Figure 20 SCB Linear Mode
0
T 0 0 0 SCB
SCB a 4
SCB a 8
SCB a 12
SCB a 16
SCB a 20
SCB a 24
SCB a 28
SCB a 32
SCB a 36
Command Word
31
16
ACK
0
CUC
R
RUC
0 0 0 0 SCB a 2
These bits specifiy the action to be performed as a result of a CA This word is set by the CPU and cleared by
the 82596 Defined bits are
Bit 31 ACK-CX
Acknowledges that the CU completed an Action Command
Bit 30 ACK-FR
Acknowledges that the RU received a frame
Bit 29 ACK-CNA
Acknowledges that the Command Unit became not active
Bit 28 ACK-RNR
Acknowledges that the Receive Unit became not ready
Bits 24–26 CUC
(3 bits) This field contains the command to the Command Unit Valid values are
0
NOP (does not affect current state of the unit)
1
Start execution of the first command on the CBL If a command is executing
complete it before starting the new CBL The beginning of the CBL is in CBL
OFFSET (address)
2
Resume the operation of the Command Unit by executing the next command
This operation assumes that the Command Unit has been previously sus-
pended
3
Suspend execution of commands on CBL after current command is complete
4
Abort current command immediately
5
Loads the Bus Throttle timers so they will be initialized with their new values
after the active timer (T-ON or T-OFF) reaches Terminal Count If no timer is
active new values will be loaded immediately This command is not valid in
82586 mode
6
Loads and immediately restarts the Bus Throttle timers with their new values
This command is not valid in 82586 mode
7
Reserved
32