Motorola MPC823e Reference Manual page 1125

IEEE 1149.1 Test Access Port
21.2 THE BOUNDARY SCAN REGISTER
The MPC823e scan chain implementation has a 397-bit boundary scan register that
contains bits for all device signal, clock pins, and associated control signals. However, the
XTAL, EXTAL, and XFC pins are associated with analog signals and are not included in the
boundary scan register. An IEEE-1149.1-compliant boundary scan register has been
included on the MPC823e. This 397-bit boundary scan register can be connected between
the TDI and TDO signals when the extest or sample / preload instructions are selected. It is
used for capturing signal pin data on the input pins, forcing fixed values on the output signal
pins, and selecting the direction and drive characteristics (a logic value or high impedance)
of the bidirectional and three-state signal pins. Figure 21-3 through Figure 21-6 depict the
various cell types.
1 — EXTEST | CLAMP
0 — OTHERWISE
G1
DATA FROM
SYSTEM
1
LOGIC MUX
1
21-4
SHIFT DR
G1
1
MUX
1
FROM LAST CELL CLOCK DR
Figure 21-3. Output Pin Cell (O.Pin)
MPC823e REFERENCE MANUAL
TO NEXT CELL
TO OUTPUT
BUFFER
D
D
C
C
UPDATE DR
MOTOROLA