
20
MPC7450 RISC Microprocessor Hardware Specifications
Electrical and Thermal Characteristics
SYSCLK to ARTRY/SHD0/SHD1 high impedance after
precharge
tKHARPZ
—2
t
sysclk
5, 8,
9, 10
Notes:
1. All input specifications are measured from the midpoint of the signal in question to the midpoint of the rising edge
of the input SYSCLK. All output specifications are measured from the midpoint of the rising edge of SYSCLK to
the midpoint of the signal in question. All output timings assume a purely resistive 50-
and output timings are measured at the pin; time-of-flight delays must be added for trace lengths, vias, and
connectors in the system.
2. The symbology used for timing specifications herein follows the pattern of t(signal)(state)(reference)(state) for inputs and
t(reference)(state)(signal)(state) for outputs. For example, tIVKH symbolizes the time input signals (I) reach the valid
state (V) relative to the SYSCLK reference (K) going to the high (H) state or input setup time. And tKHOV
symbolizes the time from SYSCLK(K) going high (H) until outputs (O) are valid (V) or output valid time. Input hold
time can be read as the time that the input signal (I) went invalid (X) with respect to the rising clock edge (KH)
(note the position of the reference and its state for inputs) and output hold time can be read as the time from the
rising edge (KH) until the output went invalid (OX).
3. The setup and hold time is with respect to the rising edge of HRESET (see
Figure 5).
4. This specification is for configuration mode select only.
5. tsysclk is the period of the external clock (SYSCLK) in nanoseconds (ns). The numbers given in the table must be
multiplied by the period of SYSCLK to compute the actual time duration (in ns) of the parameter in question.
6. Mode select signals are: BVSEL, L3VSEL, PLL_CFG[0:3], PLL_EXT, BMODE[0:1].
7. According to the bus protocol, TS is driven only by the currently active bus master. It is asserted low then
precharged high before returning to high impedance as shown in
Figure 6. The nominal precharge width for TS is
0.5
× t
SYSCLK, i.e., less than the minimum tSYSCLK period, to ensure that another master asserting TS on the
following clock will not contend with the precharge. Output valid and output hold timing is tested for the signal
asserted. Output valid time is tested for precharge.The high impedance behavior is guaranteed by design.
8. According to the bus protocol, ARTRY can be driven by multiple bus masters through the clock period immediately
following AACK. Bus contention is not an issue since any master asserting ARTRY will be driving it low. Any
master asserting it low in the first clock following AACK will then go to high impedance for one clock before
precharging it high during the second cycle after the assertion of AACK. The nominal precharge width for ARTRY
is 1.0 tsysclk; that is, it should be high impedance as shown in Figure 6 before the first opportunity for another master to assert ARTRY. Output valid and output hold timing is tested for the signal asserted.The high-impedance
behavior is guaranteed by design.
9. According to the MPX bus protocol, SHD0 and SHD1 can be driven by multiple bus masters beginning the cycle of
TS. Timing is the same as ARTRY, i.e., the signal is high impedance for a fraction of a cycle, then negated for up
to an entire cycle (crossing a bus cycle boundary) before being three-stated again. The nominal precharge width
for SHD0 and SHD1 is 1.0 tsysclk. The edges of the precharge vary depending on the programmed ratio of core to
bus (PLL configurations).
10. Guaranteed by design and not tested.
Table 10. Processor Bus AC Timing Specifications (Continued)
At recommended operating conditions. See Table 4.
Parameter
Symbol2
533, 600, 667 MHz
Unit
Notes
Min
Max