MSC8126VT8000 datasheet(22/48 Pages) FREESCALE

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MSC8126 Quad Digital Signal Processor Data Sheet, Rev. 13

Electrical Characteristics

Freescale Semiconductor

2.5.5

System Bus Access Timing

2.5.5.1

Core Data Transfers

Generally, all MSC8126 bus and system output signals are driven from the rising edge of the reference clock (REFCLK). The

REFCLK is the CLKIN signal. Memory controller signals, however, trigger on four points within a REFCLK cycle. Each cycle

is divided by four internal ticks: T1, T2, T3, and T4. T1 always occurs at the rising edge of REFCLK (and T3 at the falling

edge), but the spacing of T2 and T4 depends on the PLL clock ratio selected, as Table 13 shows.

Figure 10 is a graphical representation of Table 13.

Table 13. Tick Spacing for Memory Controller Signals

BCLK/SC140 clock

Tick Spacing (T1 Occurs at the Rising Edge of REFCLK)

1:4, 1:6, 1:8, 1:10

1/4 REFCLK

1/2 REFCLK

3/4 REFCLK

1:3

1/6 REFCLK

1/2 REFCLK

4/6 REFCLK

1:5

2/10 REFCLK

1/2 REFCLK

7/10 REFCLK

Figure 10. Internal Tick Spacing for Memory Controller Signals

REFCLK

for 1:3

for 1:5

REFCLK

for 1:4, 1:6, 1:8, 1:10

MSC8126VT8000 Datasheet(PDF) 22 Page - Freescale Semiconductor, Inc