ROM/Flash Controller
12-8
Élan™SC520 Microcontroller User’s Manual
Figure 12-4
Non-Page-Mode ROM: Fetching Four Words from a 16-Bit ROM
Figure 12-5
Page-Mode ROM: Fetching Four Doublewords (Aligned) from a 32-Bit ROM
Figure 12-6
Page-Mode ROM: Fetching Four Doublewords (Unaligned) from an 8-Bit ROM
12.5.2.4
Access Timing
Access timing is controlled in the BOOTCS or ROMCSx Control registers.
– The delay for the first access, used for both non-page-mode and page-mode, and
subsequent accesses for non-page-mode is specified in the FIRST_DLY bit field.
– The delay for subsequent accesses, for page-mode only, is specified in the SUB_DLY
bit field.
Table 12-4 shows the access timing according to the programmed wait states. These values
can be obtained using the following formula:
AccessTime = (NumberWait 1) * Period –Setup)
where:
Period is the clock period (assume 30 ns for a 33.333-MHz crystal)
Setup is assumed to be 20 ns. (It takes the actual setup time and the delay for address
changes during subsequent ROM accesses into account.)
1
3
4
- - - 0h
- - - 2h
- - - 4h
- - - 8h
GPA25–GPA0
GPD15–GPD0, or
ROMRD
BOOTCS
2
MD15–MD0
- - - 0h
- - - 4h
- - - 8h
- - - ch
1
2
3
4
GPA25–GPA0
MD31–MD0
ROMRD
BOOTCS
3
4
5
2
3
4
5
2
GPA25–GPA0
GPD7–GPD0, or
ROMRD
BOOTCS
Page crossing
MD7–MD0
Содержание Elan SC520
Страница 1: ...lan SC520 Microcontroller User s Manual Order 22004A...
Страница 4: ...iv lan SC520 Microcontroller User s Manual...
Страница 28: ...Introduction xxviii lan SC520 Microcontroller User s Manual...
Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...