AMD Geode LX CS5536 - Manual (Page 3)

AMD Geode™ LX Processor DDR2 BIOS Porting Guide 3
46959A - March 2009
Application Note
3.2 CPLD Registers
The CPLD contains two registers that indicate how it
should assert the BA[1:0], A[12:0] signals and switch
enable signals.
• If accessing the registers via I2C, the register addresses
are 80h and 81h.
• If accessing with I/O, the addresses are AC10h and
AC11h.
The two registers are defined in Table 3-1 and 3-2. Instruct-
ing the CPLD to set or clear a signal causes the behavior to
occur immediately on its outputs.
Prior to executing a LOAD MODE command, the BIOS sets
the CPLD registers to the desired pattern. The DRAM reg-
isters are programmed with the A[n] signals. The register
being initialized is determined by the pattern on BA[1:0]
(MR=00b, EMR(1)=01b, EMR(2)=10b and EMR(3)=11b).
Then the BIOS generates the LOAD MODE command by
setting, and then clearing, the PROG_DRAM bit in the
MC_CF07_DATA register. AMD also recommends setting
the MSR_BA field (same register) to the desired BA[1:0]
levels (same procedure as initializing DDR).
Table 3-1. REG_A Definition
Bit Name Description
7 A[7] Address signal 7. If SW_EN# is high, setting this bit causes the CPLD to assert the A[7] signal.
This behavior is consistent for all the A[n] and BA[n] fields.
6 A[6] Address signal 6
5 A[5] Address signal 5
4 A[4] Address signal 4
3 A[3] Address signal 3
2 A[2] Address signal 2
1 A[1] Address signal 1
0 A[0] Address signal 0
Table 3-2. REG_B Definition
Bit Name Description
7 SW_EN# Switch enable. When high, the CPLD asserts all of its A[n] and BA[n] signals, according to the
current settings in the internal registers. When low, the CPLD closes the switches and tri-states
its A[n] and BA[n] signals.
6 BA[1] Bank Address 1
5 BA[0] Bank Address 0
4 A[12] Address signal 12
3 A[11] Address signal 11
2 A[10] Address signal 10
1 A[9] Address signal 9
0 A[8] Address signal 8