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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
499 of 571
NXP Semiconductors
UM10316
Chapter 28: LPC29xx Flash/EEPROM
3.13 EEPROM wait state register
The EEPROM controller has no awareness of absolute time, while for EEPROM
operations several minimum absolute timing constraints have to be met. Therefore it can
only derive time from its clock by frequency division. The user must program the wait state
fields to appropriate values in this wait state register. These fields are -1 encoded so
programming zero will result in a one cycle wait state.
The register contains three fields, each representing a minimum duration of a phase of a
EEPROM operation. The fields have to be programmed such that:
Several (almost identical) delays of the different EEPROM operations have been put
together in these three wait state fields. This has been done to simplify the software
interface. Giving the opportunity to program every single delay separately might improve
performance a bit, but this is not enough to justify the more complex software interface.
Since programming these fields sets only "common" delays of the operations,
re-programming is not necessary when switching between the different operations.
NOTE: the wait states in the register are minus 1 encoded.
Table 431. EEPROM wait state register bit description (EEESTATE - address 0x2020 0090)
Bits
Access Reset
value
Field name Description
7:0
R/W
0x0
PHASE3
Wait states 3 (minus 1 encoded)
The number of system clock periods to meet a duration equal to the maximum of the
following delay times (see the EEPROM device specification and
):
- write operations’ min. hold time input to WE_N (t
h_i_we_n
)
- erase/program operations’ min. hold time BE_N to WE_N (t
h_be_n_we_n
)
- erase/program operations’ min. hold time input to EPP (t
h_i_epp
)
At the moment of writing this documentation the duration was 15 ns.
15:8
R/W
0x0
PHASE2
Wait states 2 (minus 1 encoded)
The number of system clock periods to meet a duration equal to the maximum of the
following delay times (see the EEPROM device specification and
):
- read operations’ max. propagation time PRECH to DO (t
p_prech_do
)
- write operation’s min. high time WE_N (t
hw_we_n
)
- erase/program operation’s min. hold time PE_N to EPP (t
h_pe_n_epp
)
At the moment of writing this documentation the duration was 55 ns.
23:16
R/W
0x0
PHASE1
Wait states 1 (minus 1 encoded)
The number of system clock periods to meet a duration equal to the maximum setup
delay time found in the read, write or erase/program operation on an EEPROM
device. See the EEPROM device specification.
At the moment of writing this documentation the duration was 35 ns.
31:24
-
0x0
reserved
waitstates
1
+
(
)
Tclk
×
duration
≥