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CHAPTER 3 SYSTEM CONTROLLER
250
Preliminary User’s Manual S14767EJ1V0UM00
3.4.6 Boot ROM
The System Controller supports up to 8MB of boot memory. This memory must be populated with either of the
following two types of memory devices:
3.4.6.1 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 200ns 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 CPU cache operations.
Table 3-6. Boot-ROM Size Configuration at Reset
RMMDR.FSM
Boot ROM Size
Address Range
00
4MB
1FC0_0000H through 1FFF_FFFH
01
8MB
1F80_0000H through 1FFF_FFFH
10
1MB
1FC0_0000H through 1FCF_FFFH
11
2MB
1FC0_0000H through 1FDF_FFFH
11
10
01
00
---
8bit
16bit
32bit
ROMSEL[1:0]
RMMDR.FSM
Byte Mode
Word Mode
Byte Mode
Word Mode
Byte Mode
00
---
---
4MB
(2Mx16bit)
2MBx2
(2Mx8bit)
2MBx2
(1Mx16bit)
1MBx4
(1Mx8bit)
01
---
---
---
---
4MBx2
(2Mx16bit)
2MBx4
(2Mx8bit)
10
---
1MB
(1Mx8bit)
---
---
---
---
11
---
2MB
(2Mx8bit)
2MB
(1Mx16bit)
1MBx2
(1Mx8bit)
---
---
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 SRMWE_B in
conjunction with SRMCS_B. When reads are performed, the controller asserts SRMOE_B in conjunction with
SRMCS_B. If the CPU 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 on the signal, if the interrupt is enabled in the NMI Mask Register “S_NMR”.
3.4.6.2 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”.
3.4.6.3 FLASH memory operations
The FLASH Memory can be programmed using following write cycle sequence by V
R
4120A. The following
commands are example of operations for the NEC
μ
PD29F800L FLASH Memory (in Byte Mode).