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IEEE 1149.1 Test Access Port
OUTPUT ENABLE
FROM SYSTEM
LOGIC
OUTPUT DATA
INPUT DATA
Figure 21-6. General Arrangement of Bidirectional Pin Cells
The value of the control bit controls the output function of the bidirectional pin. One or more
bidirectional data cells can be serially connected to a control cell. Bidirectional pins include
two scan cell for data (IO.Cell) as illustrated in Figure 21-6 and these bits are controlled by
the cell illustrated in Figure 21-5.
It is important to know the boundary scan bit order and the pins that are associated with
them. The bit order starting with the TDO output and ending with the TDI input is shown in
Table 21-1. The first column of the table defines the bit's ordinal position in the boundary
scan register. The shift register cell nearest TDO (first to be shifted in) is defined as Bit 0 and
the last bit to be shifted in is Bit 396. The second column references one of the three
MPC823e cell types depicted in Figure 21-3 through Figure 21-6 that describe the cell
structure for each type. The third column lists the pin name for all pin-related cells and
defines the name of the bidirectional control register bits. The fourth column lists the pin type
and the last column indicates the associated boundary scan register control bit for the
bidirectional output pins.
21-6
FROM LAST CELL
I/O.CTL
O.PIN
I.OBS
TO NEXT PIN PAIR
TO NEXT CELL
MPC823e REFERENCE MANUAL
I/O
EN
PIN
MOTOROLA
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