PNX17XX Datasheet, PDF (212/832 Pages) NXP Semiconductors – Connected Media Processor

Philips Semiconductors
Volume 1 of 1
PNX17xx Series
Chapter 6: Boot Module
3. Configure the MMI with default DDR SDRAM timing parameter settings that
support as many DRAM vendors as possible. It is recommended to verify these
default parameters comply with the DDR SDRAM devices used to build the
PNX17xx Series system board. Not all the MMI parameters are initialized in the
boot scripts some are the reset defaults of the MMI module. The Table 3
summarizes the values of DDR SDRAM timing parameters once the
configurations of the MMI is completed by the boot. It is then the TM5250 or the
host CPU that is in charge to fine tune these parameters by re-programming the
MMI module according to the DDR SDRAM devices used on the PNX17xx Series
system board. Furthermore ROW_WIDTH and COLUMN_WIDTH have been set
Table 3: Default DDR SDRAM Timing Parameters
Parameter
Value (Clocks)
tRCD read
4
tRCD write
4
tRRD
4
tMRD
4
tWTR
1
tWR
3
tRP
4
tRAS
9
tRFC
15
tRC
13
to 11 and 8, respectively, which allows the use of any kind of DDR SDRAM
densities and configurations during the boot process (i.e. in standalone only 8
Kilobytes of data is written to memory). Finally, some parameters are dependant
on the CAS latency of the devices. After review of different DDR SDRAM device
datasheets, it is found that devices organized in x32 support, at least, CAS
latencies of 3.0. Similarly the devices organized in x16 support at least a CAS
latencies of 2.5. In addition to the CAS latencies the x32 and x16 devices require
some different settings for the auto-precharge bit. Therefore PNX17xx Series
BOOT_MODE[3] pin is also used to determine if a x32 or x16 devices are used in
the board system. This assumption is not bullet proof but works for most of the
DDR SDRAM vendors.The boot scripts assume a x32 device when CAS latency
is 3.0 and a x16 device when the latency is 2.5. Table 4 shows the MMI
parameters affected by the BOOT_MODE[3] pin, a.k.a. CAS_LATENCY.
Table 4: CAS Latency Related DDR SDRAM Timing Parameters
Parameter
CAS_LATENCY = 3.0
CAS_LATENCY = 2.5
PRECHARGE_BIT
8
10
tCAS
6
5
PNX17XX_SER_1
Preliminary data sheet
Rev. 1 — 17 March 2006
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
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