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Electrical Characteristics

MSC8113 Tri-Core Digital Signal Processor Data Sheet, Rev. 0

Freescale Semiconductor

2.5.5

System Bus Access Timing

2.5.5.1

Core Data Transfers

Generally, all MSC8113 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 9 is a graphical representation of Table 13.

The UPM machine and GPCM machine outputs change on the internal tick selected by the memory controller configuration.

The AC timing specifications are relative to the internal tick. SDRAM machine outputs change only on the REFCLK rising edge.

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 9. Internal Tick Spacing for Memory Controller Signals

REFCLK

for 1:3

for 1:5

REFCLK

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

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