參數(shù)資料
型號: P90CE201AEB
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 16-bit microcontroller
中文描述: 16-BIT, 24 MHz, MICROCONTROLLER, PQFP64
封裝: PLASTIC, QFP-64
文件頁數(shù): 17/77頁
文件大?。?/td> 235K
代理商: P90CE201AEB
August 1993
17
Philips Semiconductors
Product specification
16-bit microcontroller
P90CE201
6
SYSTEM CONTROL
6.1
Memory mapping
The P90CE201 accesses the external ROM and RAM via
8 data lines and up to 24 address lines. Data access to or
from the memories is bytewise. The data will be split or
restructured internally to match the internal 16-bit data
format. The upper byte (bits 15 to 8) of the data is taken
from the even address, the lower byte (bits 7 to 0) from the
odd address (MSB address
+
1).
For external memory control the device provides the R/WN
signal together with chip enable signals for ROM
(CSROMN) and RAM (CSRAMN). CSROMN is activated
in the internal address range 0H to FFFFFFH. The
CSRAMN signal is activated in the internal address range
1000000H to 1FFFFFFH. In the external world RAM and
ROM are wired in parallel with a maximum address range
of 16 Mbytes each. If the larger memory of RAM or ROM
is smaller than 16 Mbytes the unused address pins can be
used as port pins. The advantages of this addressing
scheme are:
Maximum flexibility for RAM and ROM sizes.
The full physical memory size can be used without any
restrictions.
The minimum number of address pins are used.
The validity of data is signalled to the CPU by the internal
signal DTACKN. This signal is generated internally after a
programmable delay (wait states). By programming the
number of wait cycles the user can adapt the program
execution times to his memory access times. After reset
the delay for the DTACKN signal is set to its maximum
value. Programming the number of wait cycles is
described in section 6.3.2.
Fig.10 External memory interface timing - Word access.
handbook, full pagewidth
MLB004
PHI1
A0 A23
D0 D7
CSRxMN
R/WN
(Additional
Wait States)
S0
S1
S2
S3
SB
SB
S4
S5
S0
S1
S2
S3
SB
SB
S4
S5
S0
S1
byte read
byte write
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