dp83261 National Semiconductor Corporation, dp83261 Datasheet - Page 81

• Manufacturer Part Number: dp83261
• Description: Bmac Device Fddi Media Access Controller
• Manufacturer: National Semiconductor Corporation

Symbol
EA
EM
VCOPY
7 0 Signal Descriptions
7 3 2 6 External Flags
The External Flags provide input to the Ring Engine in order to set the A and C indicators or in order to initiate stripping based on
external logic
Pin
38
39
85
I O
I
I
I
External A Flag Indicates that an external address match occurred The value of EA is used to alter
the values of the transmitted A and C Indicators (Ax and Cx) EA must be valid one byte time before
EDRCVD is asserted When the EMIND bit in the Option Register is set the A Indicator is repeated as set
(S symbol) and either the Copied or Not Copied Frame Counter is incremented depending on the value of
VCOPY
External M Flag Indicates that the current frame should be stripped Three byte times after the EM
signal is asserted the Ring Engine begins to source Idle symbols and the frame is stripped
Valid Copy Indicates that the C Indicator (Cx) should be repeated as an S symbol for received frames
when VCOPY is asserted the received frame is not an SMT NSA frame received with the A indicator as
Set and
1 the internal A flag is set or
2 Option EMIND
See Section 5 5 for a complete description of the setting of the control indicators
VCOPY must be valid one byte time before EDRCVD is asserted and remain asserted until EDRCVD is
asserted
The sampled value of VCOPY with EDRCVD also affects the incrementing of the frame copied and frame
not copied counters See the description of the event counters for more information
(Continued)
e
1 and the external A flag (EA) is set
81
Description