MMC2001
STATIC RAM MODULE
MOTOROLA
REFERENCE MANUAL
6-1
SECTION 6
STATIC RAM MODULE
6.1 Overview
The static RAM (SRAM) module provides 32 Kbytes of general-purpose code and
data storage.
6.2 Functional Description
The 32-Kbyte SRAM module supports byte, halfword, and word accesses with a 32-
bit data interface to the CPU. Only the requested bytes are guaranteed to be valid on
read accesses. The SRAM acknowledges all accesses to its memory space.
The SRAM module occupies physical addresses 0x3000 0000 – 0x3000 7FFF. Echo-
ing of the SRAM block occurs throughout the region 0x3000 8000 – 0x300F FFFF; no
attempt is made to detect this condition. Accesses in the range of 0x3010 0000 –
0x3FFF FFFF result in TEA termination to the CPU.
Software designers should be aware that the echoing characteristics of this imple-
mentation may change for future versions of the M•CORE family.
The SPRAM control bit in the EIM configuration register allows selective access pro-
tection to be applied to the RAM. (See 7.7 EIM Configuration Register.) This bit
may be used to control access to the RAM based on the state of the M•CORE
PSR(S) bit. Attempted cycles to a protected RAM address space are terminated with
a TEA response to the CPU.
The SRAM module is partitioned into two independent blocks for the purposes of bat-
tery backup. An external standby power pin is provided to power both sections of the
SRAM for data retention.
The SRAM contents are undefined immediately following a power-on reset.
Table 6-1 Static RAM Module Address Map
Address
Use
Access
30000000
to
30007FFF
RAM Array
Supervisor,
Selective User
30008000
to
3000FFFF
RAM Echoes on 32-Kbyte Boundaries
Supervisor,
Selective User
30100000
to
40000000
Not Used (Access causes transfer error)
Not Applicable
Freescale Semiconductor,
I
Freescale Semiconductor, Inc.
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