UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
18 of 268
NXP Semiconductors
UM10413
MPT612 User manual
8.8 MAM usage notes
When changing MAM timing, the MAM is turned off by writing a zero to MAMCR. A new
value can then be written to MAMTIM. Finally, the MAM can be turned on again by writing
a value (1 or 2) corresponding to the desired operating mode to MAMCR.
For a system clock slower than 20 MHz, MAMTIM can be 001. A suggested flash access
time for a system clock between 20 MHz and 40 MHz is 2 CCLKs, while systems with a
system clock faster than 40 MHz, 3 CCLKs are proposed. System clocks of 60 MHz and
above require 4CCLKs.
9. Vectored
Interrupt Controller (VIC)
9.1 Features
•
ARM PrimeCell Vectored Interrupt Controller
•
32 interrupt request inputs
•
16 vectored IRQ interrupts
•
16 priority levels dynamically assigned to interrupt requests
•
Software interrupt generation
Table 9.
MAM Timing register (MAMTIM - address 0xE01F C004) bit description
Bit
Symbol
Value Description
Reset
value
2:0
MAM_fetch_
cycle_timing
000
0 - reserved
07
001
1 - MAM fetch cycles are 1 processor clock (CCLK) in
duration
010
2 - MAM fetch cycles are 2 CCLKs in duration
011
3 - MAM fetch cycles are 3 CCLKs in duration
100
4 - MAM fetch cycles are 4 CCLKs in duration
101
5 - MAM fetch cycles are 5 CCLKs in duration
110
6 - MAM fetch cycles are 6 CCLKs in duration
111
7 - MAM fetch cycles are 7 CCLKs in duration
Remark:
these bits set duration of MAM flash fetch operations as
listed. Improper setting of values can result in incorrect operation of
the device.
7:3
-
-
reserved; user software must not write logic 1s to reserved
bits; value read from a reserved bit is not defined
n/a
Table 10.
Suggestions for MAM timing selection
System clock
Number of MAM fetch cycles in MAMTIM
< 20 MHz
1 CCLK
20 MHz to 40 MHz
2 CCLK
40 MHz to 60 MHz
3 CCLK
> 60 MHz
4 CCLK