Mam Usage Notes - Philips LPC2119 User Manual

Philips Semiconductors
ARM-based Microcontroller
MAM Control Register (MAMCR - 0xE01FC000)
Two configuration bits select the three MAM operating modes, as shown in Table 38. Following Reset, MAM functions are
disabled. Changing the MAM operating mode causes the MAM to invalidate all of the holding latches, resulting in new reads of
Flash information as required.
Table 38: MAM Control Register (MAMCR - 0xE01FC000)
MAMCR Function
MAM mode
1:0
control
7:2 Reserved
MAM Timing Register (MAMTIM - 0xE01FC004)
The MAM Timing register determines how many cclk cycles are used to access the Flash memory. This allows tuning MAM timing
to match the processor operating frequency. Flash access times from 1 clock to 7 clocks are possible. Single clock Flash
accesses would essentially remove the MAM from timing calculations. In this case the MAM mode may be selected to optimize
power usage.
Table 39: MAM Timing Register (MAMTIM - 0xE01FC004)
MAMTIM Function
MAM Fetch
2:0
Cycle timing
7:3 Reserved

MAM USAGE NOTES

When changing MAM timing, the MAM must first be turned off by writing a zero to MAMCR. A new value may then be written to
MAMTIM. Finally, the MAM may be turned on again by writing a value (1 or 2) corresponding to the desired operating mode to
MAMCR.
For system clock slower than 20 MHz, MAMTIM can be 001. For system clock between 20 MHz and 40 MHz, Flash access time
is suggested to be 2 CCLKs, while in systems with system clock faster than 40 MHz, 3 CCLKs are proposed.
Memory Accelerator Module (MAM)
These bits determine the operating mode of the MAM as follows:
0 0 - MAM functions disabled.
0 1 - MAM functions partially enabled.
1 0 - MAM functions fully enabled.
1 1 - reserved
Reserved, user software should not write ones to reserved bits. The value read from a
reserved bit is not defined.
These bits set the duration of MAM Flash fetch operations as follows:
0 0 0 = 0 - Reserved.
0 0 1 = 1 - MAM fetch cycles are 1 processor clock (cclk) in duration.
0 1 0 = 2 - MAM fetch cycles are 2 processor clocks (cclks) in duration.
0 1 1 = 3 - MAM fetch cycles are 3 processor clocks (cclks) in duration.
1 0 0 = 4 - MAM fetch cycles are 4 processor clocks (cclks) in duration.
1 0 1 = 5 - MAM fetch cycles are 5 processor clocks (cclks) in duration.
1 1 0 = 6 - MAM fetch cycles are 6 processor clocks (cclks) in duration.
1 1 1 = 7 - MAM fetch cycles are 7 processor clocks (cclks) in duration.
Warning: Improper setting of this value may result in incorrect operation of the device.
Reserved, user software should not write ones to reserved bits. The value read from a
reserved bit is not defined.
LPC2119/2129/2292/2294
Description
Description
74
Preliminary User Manual
Reset
Value
0
NA
Reset
Value
0x07
NA
January 08, 2004