Electrical and Thermal Characteristics
Table 12. L3 Bus Interface AC Timing Specifications for MSUG2 (continued)
At recommended operating conditions. See Table 4.
8
All Speed Grades
Parameter
Symbol
Unit Notes
L3OH0 = 0, L3OH1 = 0 L3OH0 = 0, L3OH1 =1 L3OH0 = 1, L3OH1 = 0 L3OH0 = 1, L3OH1 = 1
Min
Max
Min
Max
Min
Max
Min
Max
L3_CLK to
high
tL3CHOZ
—
tL3_CLK/4
+ 2.0
—
tL3_CLK/4
+ 2.0
tL3_CLK/4
+ 2.0
—
tL3_CLK/4
+ 2.0
—
ns
impedance:
All other
outputs
Notes:
1. Rise and fall times for the L3_CLK output are measured from 20% to 80% of GV
.
DD
2. For DDR, all input specifications are measured from the midpoint of the signal in question to the midpoint voltage of the rising
or falling edge of the input L3_ECHO_CLKn (see Figure 10). Input timings are measured at the pins.
3. For DDR, the input data will typically follow the edge of L3_ECHO_CLKn as shown in Figure 10. For consistency with other
input setup time specifications, this will be treated as negative input setup time.
4. t
/4 is one-fourth the period of L3_CLKn. This parameter indicates that the MPC7455 can latch an input signal that is
L3_CLK
valid for only a short time before and a short time after the midpoint between the rising and falling (or falling and rising) edges
of L3_ECHO_CLKn at any frequency.
5. All output specifications are measured from the midpoint voltage of the rising (or for DDR write data, also the falling) edge
of L3_CLK to the midpoint of the signal in question. The output timings are measured at the pins. All output timings assume
a purely resistive 50-Ω load (see Figure 8).
6. For DDR, the output data will typically lead the edge of L3_CLKn as shown in Figure 10. For consistency with other output
valid time specifications, this will be treated as negative output valid time.
7. t
/4 is one-fourth the period of L3_CLKn. This parameter indicates that the specified output signal is actually launched
L3_CLK
by an internal clock delayed in phase by 90°. Therefore, there is a frequency component to the output valid and output hold
times such that the specified output signal will be valid for approximately one L3_CLK period starting three-fourths of a clock
prior to the edge on which the SRAM will sample it and ending one-fourth of a clock period after the edge it will be sampled.
8. These configuration bits allow the AC timing of the L3 interface to be altered via software. L3OH0 = L2CR[12],
L30H1 = L3CR[12]. Revisions of the MPC7455 not described by this document may implement these bits differently. See
Section 11.1, “Part Numbers Fully Addressed by This Document,” and Section 11.2, “Part Numbers Not Fully Addressed by
This Document,” for more information on which devices are addressed by this document.
MPC7455 RISC Microprocessor Hardware Specifications, Rev. 4.1
24
Freescale Semiconductor
FREESCALE [ Freescale ]
