Information

Enhanced Local Bus Controller
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 10-77
24 LOOP Loop start/end. The first RAM word in the RAM array where LOOP is 1 is recognized as the loop
start word. The next RAM word where LOOP is 1 is the loop end word. RAM words between,
and including the start and end words, are defined as part of the loop. The number of times the
UPM executes this loop is defined in the corresponding loop fields of the MxMR.
0 The current RAM word is not the loop start word or loop end word.
1 The current RAM word is the start or end of a loop.
25 EXEN Exception enable. Allows branching to an exception pattern at the exception start address
(EXS). When an internal bus monitor time-out exception is recognized and EXEN in the RAM
word is set, the UPM branches to the special exception start address (EXS) and begins
operating as the pattern defined there specifies.
The user should provide an exception pattern to negate signals controlled by the UPM in a
controlled fashion. For DRAM control, a handler should negate RAS and CAS to prevent data
corruption. If EXEN = 0, exceptions are ignored by UPM (but not by local bus) and execution
continues. After the UPM branches to the exception start address, it continues reading until the
LAST bit is set in the RAM word.
0 The UPM continues executing the remaining RAM words, ignoring any internal bus monitor
time-out.
1 The current RAM word allows a branch to the exception pattern after the current cycle if an
exception condition is detected.
26–27 AMX Address multiplexing. Determines the source of LAD during an LALE phase. Any change in the
AMX field initiates a new LALE (address) phase.
00 LAD (and/or in conjunction with LA) is the non-multiplexed address. For example, column
address.
01 Reserved
10 LAD (and/or in conjunction with LA) is driven with the multiplexed address according to
MxMR[AM]. For example, row address. See Section 10.4.4.4.7, “Address Multiplexing
(AMX)” for more information.
11 LAD (and/or in conjunction with LA) is driven with the contents of MAR. Used, for example,
to initialize a mode.
Note: Source ID debug mode is only supported for the AMX = 00 setting.
Note: AMX must not change values in any RAM word which begins a loop.
28 NA Next burst address. Determines when the address is incremented during a burst access.
0 The address increment function is disabled.
1 The address is incremented in the next cycle. In conjunction with the BRn[PS], the increment
value of LAn is 1 or 2 for port sizes of 8 and 16 bits, respectively.
29 UTA UPM transfer acknowledge. Indicates assertion of transfer acknowledge in the current cycle.
0 Transfer acknowledge is not asserted in the current cycle.
1 Transfer acknowledge is asserted in the current cycle.
In case of UPM writes, program UTA and LAST in same RAM word.
In case of UPM reads, program UTA and LAST in consecutive or same RAM words.
30 TODT Turn-on disable timer. The disable timer associated with each UPM allows a minimum time to
be guaranteed between two successive accesses to the same memory bank. This feature is
critical when DRAM requires a RAS precharge time. TODT turns the timer on to prevent another
UPM access to the same bank until the timer expires.The disable timer period is determined in
MxMR[DSn]. The disable timer does not affect memory accesses to different banks. Note that
TODT must be set together with LAST, otherwise it is ignored.
0 The disable timer is turned off.
1 The disable timer for the current bank is activated preventing a new access to the same bank
(when controlled by the UPMs) until the disable timer expires. For example, precharge time.
Table 10-40. RAM Word Field Descriptions (continued)
Bits Name Description