ARM R4F, r1p3 manual Data cache RAM bits, with parity Description

Level One Memory System

Table 8-12 Data cache data RAM sizes, with parity

Cache size		Data RAMs
4KB, 4 1KB ways		8 banks 36 bits 128 lines
8KB, 4 2KB ways		8 banks 36 bits 256 lines
16KB, 4	4KB ways	8 banks 36 bits 512 lines
32KB, 4	8KB ways	8 banks 36 bits 1024 lines
64KB, 4	16KB ways	8 banks 36 bits 2048 lines

Table 8-13shows the organization of the data cache RAM bits when parity is implemented.

Table 8-13 Data cache RAM bits, with parity

RAM bits	Description
Bit [35]	Parity bit for byte[31:24]
Bit [34]	Parity bit for byte[23:16]
Bit [33]	Parity bit for byte[15:8]
Bit [32]	Parity bit for byte[7:0]
Bits [31:0]	Data[31:0]

Parity bits are grouped together in bits[35:32] so that data and parity bits are easily differentiated. With this design the parity bit is selected alongside the related data byte, so that when data is updated, the parity bit is also updated.

Data RAM sizes with ECC implemented

Table 8-14shows the organization for the instruction cache when ECC is implemented. For ECC error detection, eight bits are added per 64 bits, so four bits are added for each RAM bank.

Table 8-14 Instruction cache data RAM sizes with ECC

Cache size		Data RAMs
4KB, 4 1KB ways		4 banks 72 bits 128 lines or
		8 banks 36 bits 128 lines
8KB, 4 2KB ways		4 banks 72 bits 256 lines or
		8 banks 36 bits 256 lines
16KB, 4	4KB ways	4 banks 72 bits 512 lines or
		8 banks 36 bits 512 lines
32KB, 4	8KB ways	4 banks 72 bits 1024 lines or
		8 banks 36 bits 1024 lines
64KB, 4	16KB ways	4 banks 72 bits 2048 lines or
		8 banks 36 bits 2048 lines

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