am79c864a Advanced Micro Devices, am79c864a Datasheet - Page 20

• Manufacturer Part Number: am79c864a
• Description: Physical Layer Controller With Scrambler Plc-s
• Manufacturer: Advanced Micro Devices

3-22
01–00 PCM_CNTRL
Bit
AMD
Name
Definition
PCM_CNTRL controls the PCM state machine. When set to a value other than zero, it
will cause the PCM to immediately make a transition to the BREAK, TRACE or OFF
state. The transition to the BREAK or OFF state will occur regardless of the state the
PCM is in at the time. The transition to the TRACE state will only be made if the PCM is
in the ACTIVE state, otherwise PCM_CNTRL will be ignored. The following table
describes the action taken according to the value of the two bits:
PCM_CNTRL
00
01
10
11
After a PC_Start (PCM_CNTRL=01) has been issued and before another one can be
issued, PCM_CNTRL must first be written with zero and then written with the PC_Start
value again. Note that if the PCM goes to the BREAK state for a reason other than
writing PCM_CNTRL (e.g. QLS is received, or a timeout occurs), the PCM will
not go to the CONNECT state and will remain in the BREAK state until PCM_CNTRL is
written with the PC_Start value. If the PCI is in the INSERTED state when PC_Start or
PC_Stop is issued, scrubbing will be performed. If the PCI is in the
INSERT_SCRUB or REMOVE_SCRUB state when PC_Start or PC_Stop is issued,
the scrubbing will be completed before the PCM enters the BREAK or OFF state.
The SUPERNET 2 Family for FDDI 1994 Data Book
Table 3. PLC_CNTRL_B (continued)
P R E L I M I N A R Y
Description
The PCM state is not affected
The PCM goes to the BREAK state (PC_Start)
The PCM goes to the TRACE state (PC_Trace)
The PCM goes to the OFF state (PC_Stop)