MPC7448 查看數據表（PDF） - Freescale Semiconductor

零件编号

产品描述 (功能)

生产厂家

MPC7448

RISC Microprocessor Hardware Specifications

Freescale Semiconductor 

Electrical and Thermal Characteristics

Table 9. Processor Bus AC Timing Specifications1 (continued)

At recommended operating conditions. See Table 4.

Parameter

All Speed Grades

Symbol 2

Unit

Notes

Min

Max

SYSCLK to output high impedance (all except TS, ARTRY,

SHD0, SHD1)

tKHOZ

—

1.8

ns

5

SYSCLK to TS high impedance after precharge

Maximum delay to ARTRY/SHD0/SHD1 precharge

SYSCLK to ARTRY/SHD0/SHD1 high impedance after

precharge

tKHTSPZ

—

tKHARP

—

tKHARPZ

—

1

tSYSCLK 3, 4, 5

1

tSYSCLK 3, 5, 6, 7

2

tSYSCLK 3, 5, 6, 7

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-Ω load (see Figure 4). Input 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. tsysclk is the period of the external clock (SYSCLK) in 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.

4. According to the bus protocol, TS is driven only by the currently active bus master. It is asserted low and precharged high

before returning to high impedance, as shown in Figure 6. The nominal precharge width for TS is tSYSCLK, that is, one clock

period. Since no master can assert TS on the following clock edge, there is no concern regarding contention 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.

5. Guaranteed by design and not tested

6. 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 because 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 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 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.

7. According to the MPX bus protocol, SHD0 and SHD1 can be driven by multiple bus masters beginning two cycles after TS.

Timing is the same as ARTRY, that is, 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).

8. BMODE[0:1] and BVSEL[0:1] are mode select inputs. BMODE[0:1] are sampled before and after HRESET negation.

BVSEL[0:1] are sampled before HRESET negation. These parameters represent the input setup and hold times for each

sample. These values are guaranteed by design and not tested. BMODE[0:1] must remain stable after the second sample;

BVSEL[0:1] must remain stable after the first (and only) sample. See Figure 5 for sample timing.

MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

18

Freescale Semiconductor

Share Link: