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Download LH7A404 User`s Guide.book
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Core and Data Paths LH7A404 User’s Guide 3.1.5 Boot Modes The LH7A404 can boot from either SynchFlash, internal ROM, external Asynchronous ROM, or external Flash memory. The boot mode is specified at power-on reset by the Media Change signal (MEDCHG, pin E4) and the Boot Width signals (WIDTH[1:0], pins W13 and Y13, respectively) and the Internal Boot pin (INTBOOT, pin Y20). The signal values for each boot mode are shown in Table 3-1. The boot mode determines the memory mapping, as shown in Figure 3-3. To boot from external Synchronous memory, configure the WIDTH and MEDCHG signals to map SDMC Bank 3 (nSCS3) to memory location 0x0000.0000. To boot from external Asynchronous memory, map SMC Bank 0 (nCS0) to memory location 0x0000.0000. Booting from the internal ROM is described in the next section. After the LH7A404 has booted, software can reconfigure the mapping. Table 3-1. Boot Mode Signals BOOT MODE WIDTH [1:0] MEDCHG INTBOOT 8-bit ROM 00 0 0 16-bit ROM 01 0 0 32-bit ROM 10 0 0 Invalid: Do not allow this condition. 11 0 0 16-bit SynchFlash (Initializes device MODE Register) 00 1 0 16-bit SROM (Initializes device MODE Register) 01 1 0 32-bit SynchFlash (Initializes device MODE Register) 10 1 0 32-bit SROM (Initializes device MODE Register) 11 1 0 Boot from internal Boot ROM; see Chapter 4 xx x 1 3.1.5.1 Internal Boot ROM Booting from on-chip ROM can also be selected by tying the INTBOOT pin HIGH. See Chapter 4 for details about using the internal Boot ROM. 3-6 Ver. 1.3 — 27 August 2007 NXP Semiconductors
