SPNS174
–
SEPTEMBER 2011
4.11 Tightly-Coupled RAM Interface Module
illustrates the connection of the Tightly Coupled RAM (TCRAM) to the Cortex-R4F™ CPU.
VBUSP I/F
PMT I/F
Upper 32 bits data &
4 ECC bits
EVEN Address
TCM BUS
64 Bit data bus
36 Bit
3636 Bit
Bit
wide
wide
wide
RAM
RAM
RAM
36 Bit
3636 Bit
Bit
wide
wide
wide
RAM
RAM
RAM
Cortex R4F™
B0
TCM
A
TCM
TCRAM
Interface 1
Lower 32 bits data &
4 ECC bits
B1
TCM
ODD Address
TCM BUS
64 Bit data bus
Upper 32 bits data &
4 ECC bits
36 Bit
wide
36
36 Bit
Bit
wide
RAM
wide
RAM
RAM
36 Bit
36
36 Bit
Bit
wide
wide
wide
RAM
RAM
RAM
TCRAM
Interface 2
Lower 32 bits data &
4 ECC bits
PRODUCT PREVIEW
VBUSP I/F
PMT I/F
Figure 4-10. TCRAM Block Diagram
4.11.1 Features
The features of the Tightly Coupled RAM (TCRAM) Module are:
•
Acts as slave to the Cortex-R4F CPU's BTCM interface
•
Supports CPU's internal ECC scheme by providing 64-bit data and 8-bit ECC code
•
Monitors CPU Event Bus and generates single or multi-bit error interrupts
•
Stores addresses for single and multi-bit errors
•
Supports RAM trace module
•
Provides CPU address bus integrity checking by supporting parity checking on the address bus
•
Performs redundant address decoding for the RAM bank chip select and ECC select generation logic
•
Provides enhanced safety for the RAM addressing by implementing two 36-bit wide byte-interleaved
RAM banks and generating independent RAM access control signals to the two banks
•
Supports auto-initialization of the RAM banks along with the ECC bits
4.11.2 TCRAMW ECC Support
The TCRAMW passes on the ECC code for each data read by the Cortex-R4F CPU from the RAM. It also
stores the CPU's ECC port contents in the ECC RAM when the CPU does a write to the RAM. The
TCRAMW monitors the CPU's event bus and provides registers for indicating single/multi-bit errors and
also for identifying the address that caused the single or multi-bit error. The event signaling and the ECC
checking for the RAM accesses must be enabled inside the CPU.
For more information see the RM48x Technical Reference Manual (SPNU481).
4.12
Parity Protection for Accesses to peripheral RAMs
Accesses to all peripheral RAMs are protected by odd/even parity checking. During a read access the
parity is calculated based on the data read from the peripheral RAM and compared with the good parity
value stored in the parity RAM for that peripheral. If any word fails the parity check, the module generates
a parity error signal that is mapped to the Error Signaling Module. The module also captures the
peripheral RAM address that caused the parity error.
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System Information and Electrical Specifications
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2011, Texas Instruments Incorporated
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