13 boot rom – NEC Network Controller uPD98502 User Manual
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CHAPTER 3 SYSTEM CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM
213
3.4.13 Boot ROM
The system controller supports up to 8 MB of boot memory. This memory must be populated with either of the
following two types of memory devices: PROM/flash memory.
3.4.13.1 Boot ROM configuration and address ranges
Boot ROM can be populated with PROM or 85-ns flash chips, and it must have an access time of 200 ns or less.
The system controller supports 8, 16 and 32-bit boot ROM at locations 1F80_0000H through 1FFF_FFFFH in the
physical memory space on V
R
4120A. The boot ROM does not support V
R
4120A cache operations.
Table 3-6. Boot-ROM Size Configuration at Reset
RMMDR.FSM
Boot ROM Size
Address Range
00
4 MB
1FC0_0000H through 1FFF_FFFH
01
8 MB
1F80_0000H through 1FFF_FFFH
10
1 MB
1FC0_0000H through 1FCF_FFFH
11
2 MB
1FC0_0000H through 1FDF_FFFH
The controller asserts the flash/ROM chip select (SRMCS_B) in the address range 1F80_0000H through
1FFF_FFFFH. When writes are performed to the ROM/flash memory space, the controller asserts SDWE_B in
conjunction with SRMCS_B. When reads are performed, the controller asserts SRMOE_B in conjunction with
SRMCS_B. If the V
R
4120A attempts to access boot ROM addresses outside the defined size of the flash/ROM, the
controller returns 0 with the data error bit set on SysCMD [0]. In addition, the NMI status register “S_NSR” is updated
and NMI is asserted to V
R
4120A, if the interrupt is enabled in the NMI enable register “S_NER”.
3.4.13.2 Flash memory write-protection
The flash memory can be protected in software. Software protection is implemented by programming the WM field
in ROM mode register “RMMDR”.
3.4.13.3 Flash memory operations
Flash memory I/F has 3 modes for each Flash data BUS size, that is 8,16 and 32 bits. And on the case of each Bus
size, the way of causing write cycle will be changed. The flash memory can be programmed using following write
cycle sequence by V
R
4120A. The following commands are example of operations for the AMD AM29LV800BT flash
memory (using Byte Mode) at 32-bit Flash data Bus mode in System Controller.