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

AHB Components3.16 64-bit to 32-bit downsizerThe AHB downsizer module, Downsizer64, converts 64-bit wide AHB master data busesto narrower 32-bit slave AHB data buses. The downsizer module reduces the width ofthe data bus by half from an AHB master to an AHB slave. You can use full-widthmaster transfers. This process involves modification of the transfer type, burst, and size,and latching half of the master read data. In addition, multiple slave writes or readsmight be required to transfer data to and from the narrow slave.Figure 3-40 shows the signal interface of the downsizer module.HCLKHRESETnDownsizer64-bitAHB busHADDRS[31:0]HSELSHTRANSS[1:0]HSIZES[2:0]HBURSTS[2:0]HWRITESHPROTS[3:0]HMASTLOCKSHWDATAS[63:0]HREADYSHREADYOUTSHRESPS[1:0]HRDATAS[63:0]AHBslaveinterfaceAHBmasterinterfaceHADDRM[31:0]HSELMHTRANSM[1:0]HSIZEM[2:0]HBURSTM[2:0]HWRITEMHPROTM[3:0]HMASTLOCKMHWDATAM[31:0]HREADYMHREADYOUTMHRESPM[1:0]HRDATAM[31:0]32-bitAHB busFigure 3-40 Downsizer module3.16.1 Programmer's modelProgramming details for the downsizer are described in the following sections:• Downsizer transfers on page 3-86• Unsupported transfers on page 3-88• Burst blocking after error on page 3-88• Slave responses on page 3-89• Modification of control signals on page 3-89.ARM DDI 0243C Copyright © 2003, 2007 ARM Limited. All rights reserved. 3-85