I have a question about how MC9328MXL/1 initializes SDRAM memories. These is the instructions used to set up the Mode Command Register (file board/mx1ads/lowlevel_init.S) for MX1ADS evalutaion board:
/* Issue Mode Register Command */ ldr r3, =0x08111800 /* Mode Register Value */ ldr r2, [r3]
In my understanding address lines are connected as follows:
SDRAM -> MC9328MXL ------------------- A12 -> A13 A11 -> A12 A10 -> MA11 A9 -> MA10 A8 -> A10 A7 -> A9 A6 -> A8 A5 -> A7 A4 -> A6 A2 -> A5 A1 -> A3 A0 -> A2
Thus, when writing to address 0x08111800, microprocessor address lines from A8 to A6 are set to 0. It implies that SDRAM address lines from A6 to A4 are set to 0. These lines are decoded by the SDRAM chips as CAS latency. Allowed values are 010 (CAS latency = 2) and 011 (CAS latency = 3). The value 000 is reserved. So I think I'm misunderstanding how the SDRAM controller works. Anybody can help me?
Thanks in advance, llandre
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