MC68332
STANDBY RAM WITH TPU EMULATION
USER’S MANUAL
8-1
SECTION 8 STANDBY RAM WITH TPU EMULATION
The standby RAM module with TPU emulation capability (TPURAM) consists of a con-
trol register block and a 2-Kbyte array of fast (two bus cycle) static RAM, which is es-
pecially useful for system stacks and variable storage. The TPURAM responds to both
program and data space accesses. The TPURAM can be used to emulate TPU micro-
code ROM.
8.1 General
The TPURAM can be mapped to any 2-Kbyte boundary in the address map, but must
not overlap the module control registers. Refer to
for more information. Data can be read or written in bytes, words or long words.
The TPURAM is powered by V
DD
in normal operation. During power-down, TPURAM
contents can be maintained by power from the V
STBY
input. Power switching between
sources is automatic.
8.2 TPURAM Register Block
There are three TPURAM control registers: the TPURAM module configuration regis-
ter (TRAMMCR), the TPURAM test register (TRAMTST), and the TPURAM base ad-
dress and status register (TRAMBAR). To protect these registers from accidental
modification, they are always mapped to supervisor data space.
The TPURAM control register block begins at address $7FFB00 or $FFFB00, depend-
ing on the value of the module mapping (MM) bit in the SIM configuration register
SECTION 4 SYSTEM INTEGRATION MODULE
contains more information
about how the state of MM affects the system.
There is a 64-byte minimum control register block size for the TPURAM module. Un-
implemented register addresses are read as zeros, and writes have no effect. Refer
for the register block address map and reg-
ister bit/field definitions.
8.3 TPURAM Array Address Mapping
Base address and status register TRAMBAR specifies the TPURAM array base ad-
dress in the MCU memory map. TRAMBAR[15:3] specify the 13 MSBs of the base ad-
dress. The TPU bus interface unit compares these bits to address lines ADDR[23:11].
If the two match, then the low order address lines and the SIZ[1:0] signals are used to
access the RAM location in the array. The TPURAM can be mapped to any 2-Kbyte
boundary in the address map, but must not overlap the module control registers. Over-
lap makes the registers inaccessible.
The RAM disable (RAMDS) bit, the LSB of the TRAMBAR, indicates whether the
TPURAM array is active (RAMDS = 0) or disabled (RAMDS = 1). The array is disabled
coming out of reset and remains disabled if the base address field is programmed with
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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