AMBA Design Kit Technical Reference Manual - ARM Information ...

Behavioral Models5.3 External ROMThe external ROM module, ExtROM, is a simple model of a 16K x 8 off-chip EPROM,that can be initialized with data from a local file. Figure 5-3 shows the external ROMmodule.A[13:0]CEnOEnExtROMQ[7:0]Figure 5-3 External ROM module interface diagram5.3.1 Programmer’s modelTable 5-4 lists the user-defined settings for the external ROM module.Table 5-4 User-defined settings for the external ROM moduleSignalTypeDefaultsettingDescriptionFILENAME Input filename - This signal points to the local input data file that is read in after reset.ROMDEPTH Memory depth 16 This signal sets the memory depth in KB. If the value is increased fromthe default setting, then the address input bus A must also be increased toenable all memory to be addressed.5.3.2 Signal descriptionsTable 5-5 lists the non-AMBA signals used by the external ROM module.Signal Type Direction DescriptionA[13:0] External address Input The external address inputTable 5-5 External ROM module signalsCEN Chip enable Input When LOW, this signal indicates that the chip has been selectedand must respond to the current transferOEN Output enable Input When LOW, this signal indicates a read transfer, and enables themodule to drive data onto QQ[7:0] External data out Output The external data bus, driven during read transfers5-6 Copyright © 2003, 2007 ARM Limited. All rights reserved. ARM DDI 0243C