Motorola MPC860 PowerQUICC User Manual page 350

Part IV. Hardware Interface
Mode as a default. When required, a debug mode controller tool externally drives this signal
high actively to put the MPC860 into debug mode.
Two pins need special attention, depending on the version of MPC860 used (as noted in
Section 13.4, ÒRecommended Basic Pin Connections.Ó)
¥ For MPC860 rev B and later, TDI/DSDI should be pulled up to VCC to keep it from
oscillating when unused.
¥ For MPC860 rev A.3 and earlier, TCK/DSCK should be connected to ground if it is
conÞgured for its DSCK function, as stated above. However, for these versions of
the MPC860, the pull-down resistor must be strong (for example, 1 kW) to overcome
the internal pull-up resistor.
To allow application of any version of processor, perform both of the above actions.
13.4.3 Unused Inputs
In general, pull-up resistors should be used on any unused inputs to keep them from
oscillating. For example, if PCMCIA is not used, the PCMCIA input pins (WAIT_A,
WAIT_B, IP_A[0Ð8], IP_B[0Ð8]) should have external pull-up resistors. However, unused
pins of port A, B, C, or D can be conÞgured as outputs, and, if they are conÞgured as outputs
they do not require external terminations.
13.4.4 Unused Outputs
Unused outputs can be left unterminated.
13.5 Signal States during Hardware Reset
During hardware reset (HRESET or PORESET), the signals of the MPC860 behave as
follows:
¥ The bus signals are high-impedance.
¥ The port I/O signals are conÞgured as inputs, and are therefore high-impedance.
¥ The memory controller signals are driven to their inactive state.
However, some signal functions are determined by the reset conÞguration. When HRESET
is asserted, these signals immediately begin functioning as determined by the reset
conÞguration and are either high-impedance or are driven to their inactive state
accordingly. The behavior of these signals is shown in Table 13-3.
13-24 MPC860 PowerQUICC UserÕs Manual MOTOROLA