COBHAM GR740 - Sdram Configuration Register

GR740-UM-DS, Nov 2017, Version 1.7 108 www.cobham.com/gaisler
GR740
10.6.1 SDRAM configuration register 1
Table 95. 0x00 - SDCFG1 - SDRAM configuration register 1
31 30 29 27 26 25 23 22 21 20 18 17 16 15 14 0
RF tRP tRFC tC BANKSZ COLSZ COMMAND R MS 64 RFLOAD
0 1 0b111 1 0b000 10 0 0 0 * NR
rw rw rw rw rw rw rw r r r rw
31 SDRAM refresh (RF) - If set, the SDRAM refresh will be enabled.
30 SDRAM tRP timing (tRP) - tRP will be equal to 2 or 3 system clocks (0/1). When mobile SDRAM
support is enabled, this bit also represent the MSB in the tRFC timing.
29: 27 SDRAM tRFC timing (tRFC) - tRFC will be equal to 3 + field-value system clocks. When mobile
SDRAM support is enabled, this field is extended with the bit 30.
26 SDRAM CAS delay (tC) - Selects 2 or 3 cycle CAS delay (0/1). When changed, a LOAD-COM-
MAND-REGISTER command must be issued at the same time. Also sets RAS/CAS delay (tRCD).
25: 23 SDRAM banks size (BANKSZ) - Defines the decoded memory size for each SDRAM chip select,
excluding check bits:
In half-width mode: "000" = 4 Mbyte, "001" = 8 Mbyte, "010" = 16 Mbyte .... "111" = 512 Mbyte.
In full-width mode: "000" = 8 Mbyte, "001"= 16 Mbyte, "010" = 32 Mbyte .... "111" = 1024 Mbyte.
Note: In silicon revision 0 the behaviour of this field is always as described for half-width mode
above. See section 43 for additional information.
22: 21 SDRAM column size (COLSZ) - “00”=256, “01”=512, “10”=1024, “11”=4096 when bit[25:23]=
“111”, 2048 otherwise.
20: 18 SDRAM command (COMMAND) - Writing a non-zero value will generate an SDRAM command:
“010”=PRECHARGE, “100”=AUTO-REFRESH, “110”=LOAD-COMMAND-REGISTER. The
field is reset after command has been executed.
17 RESERVED
16 Mobile SDRAM support (MS) - Disabled
15 64-bit data bus (64) - Reads ‘1’ if memory controller is configured for 64-bit data bus, otherwise ‘0’.
Read-only. Affected by value of MEM_IFWIDTH bootstrap signal.
14: 0 Refresh counted reload value (RFLOAD) - The period between each AUTO-REFRESH command -
Calculated as follows: tREFRESH = ((reload value) + 1) / SYSCLK