Transmitter Fault Count; Private Area Function Code; Private Area Pointer; Parameters Initializing The Private Area - Motorola MC68824 User Manual

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revision while the '2' means the TBC implements 802.4 Revision 2. This parameter may be read
via the READ VALUE command.
2.1.27 Transmitter Fault Count
The transmitter fault count is an integer in the range from zero to seven stored by the TBC in the
most significant three bits. If the station sequences to the end of the token contention process
and loses, or fails to pass the token to any successor, this counter is incremented by one. If this
value exceeds seven, bit 1 of interrupt status word 1 will be set by the TBC (see 2.2.11 Interrupt
Status Words for a complete description). This parameter may be read via the READ VALUE
command.
Offset
7A
TX FCNT
o
2.2 INITIALIZATION TABLE
'.
C B A
1 0
o
I
0
I
0
o
I
0
I
0
o
I
0
I
0
o
I
0
The initialization table is a 256-byte area of memory which is shared by the TBC and the host
CPU. It is used by the host processor to pass operating parameters and pointers to the TBC. This
is performed during the initialization sequence and whenever it is necessary to update operating
parameters during TBC operation. The initialization table is also used by the TBC to pass status,
statistic counters, and command return information (parameters) to the host.
The format of the initialization table is shown in Figure 2-3.
2.2.1 Private Area Function Code
Bits 0-3 of the initialization table word 0 contain the function code values that may be required
by the system to access the private area. If no function codes are used, this word does not need
to be initialized by the host. The TBC private area pointer is located in the subsequent two words
of the initialization table.
Offset F E D C
00 10101010
2.2.2 Private Area Pointer
B A
o
I
0
4
I
0
o
I
0
Private Area FC
The private area pointer is a 32-bit address which points to the 128-byte area in RAM that should
only be accessed by the TBC since it contains MAC variables and parameters.
Offset F
o
C B A
4
02 'IM-S-B--------------------P-riv-at-e-Ar-ea-P-oi-nte-r---H-i9-h-W-or-d--------------------~
04
Private Area Pointer - Low Word
LSB I
2.2.3 Parameters Initializing the Private Area
The parameters in displacements 08-76 are the initial values of the corresponding parameters of
the private area. These values are initialized by the host CPU in the intialization table and are then
loaded into the private area by the INITIALIZE command. For a detailed description of these
parameters, see 2.1 TBC PRIVATE AREA.
MOTOROLA
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MC68824 USER'S MANUAL