IEEE 1149.1 Test Access Port
21-6
MPC823e REFERENCE MANUAL
MOTOROLA
IEEE 1149.1 TEST
21
ACCESS PORT
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.
Figure 21-6. General Arrangement of Bidirectional Pin Cells
I/O
PIN
FROM LAST CELL
OUTPUT DATA
INPUT DATA
OUTPUT ENABLE
I.OBS
EN
FROM SYSTEM
LOGIC
O.PIN
I/O.CTL
TO NEXT PIN PAIR
TO NEXT CELL
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