Motorola MPC823e Reference Manual page 413

15.5.4.2.2 Chip-Select Signals. The MS field in the base register of the accessed memory
bank selects a user-programmable machine on the currently requested cycle. The selected
UPM only affects the assertion and negation of the appropriate CSx signal and its timing is
specified in the UPM RAM word. Figure 15-28 illustrates how the CSx signals are controlled
by the UPMs.
UPMA
UPMB
GPCM
Note: The UPM refresh is done in a round robin manner. If more than one chip-select
uses the same UPM, the refreshes will progress through each one. For example,
if you have three chip-selects using UPMA, you would need to set the periodic
timer A period to one-third the normal refresh.
MOTOROLA
BANK SELECTED
MS[0:1] IN BRx
MUX
Figure 15-28. CSx Signal Selection
MPC823e REFERENCE MANUAL
Memory Controller
CS0
CS1
CS2
CS3
SWITCH
CS4
CS5
CS6
CS7
MS[0:1]
MACHINE
00 GPCM
01
—
10 UPMA
11 UPMB
15-55