II CORE BLOCK: BCU (Bus Control Unit)
31 | Destination | 0 |
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| Bus operation |
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| Sign or Zero extension |
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| Byte 0 |
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| No. | A1 | A0 | #WRH #WRL | 15 | Data bus | 0 |
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| 8 |
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| 1 | 0 |
| 1 | ∗ | ∗ | X | 1 |
| Ignored | Byte 0 |
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| A[1:0]=∗∗ |
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| Source |
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| (X: Not connected/Unused) |
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31 | Destination | 0 |
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| Bus operation |
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| Sign or Zero extension |
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| Byte 0 |
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| No. | A1 | A0 | #WRH #WRL | 15 | Data bus | 0 |
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| 8 |
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| 1 | 0 |
| 1 | ∗ | ∗ | 1 | 1 |
| Byte 0 | Ignored |
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| A[1:0]=∗∗ |
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Source
Figure 4.16 Byte Data Reading from an
Bus Clock
The bus clock is generated by the BCU using the CPU system clock output from the clock generator. Figure 4.17 shows the clock system.
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| To CPU | |||
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| PLLS[1:0] pins |
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| #X2SPD pin |
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| CLG |
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| Bus clock | |||
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| CLKDT[1:0] |
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| CLKCHG |
| BCU |
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OSC3_CLK |
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| BCLKSEL[1:0] |
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oscillation circuit |
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| CPU_CLK |
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| BCU_CLK |
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| PLL_CLK |
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| A |
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| 1/1 or 1/2 |
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| BCLK pin | |||
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PLL |
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OSC3_CLK (PLL: off)
PLL_CLK (PLL: x2 mode)
PLL_CLK (PLL: x4 mode)
(when the CPU system clock source is OSC3)
A CPU_CLK (CLKDT = 1/1) CPU_CLK (CLKDT = 1/2) CPU_CLK (CLKDT = 1/4) CPU_CLK (CLKDT = 1/8)
CPU_CLK |
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BCU_CLK(#X2SPD=H, x1 speed mode) |
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| ∗ 1 |
| ∗ 1 |
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| ∗ 2 |
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| ∗ 1 |
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| ∗ 2 |
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BCU_CLK(#X2SPD=L, x2 speed mode) |
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| ∗ 1 |
| ∗ 1 |
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| ∗ 2 |
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| ∗ 1 |
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| ∗ 1 | Access to the internal RAM | ||||||||||||||||
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| ∗ 2 | Access to the external memory |
Figure 4.17 Clock System
EPSON | S1C33210 FUNCTION PART |