3.16.2. Signal descriptions

Table 3.44 lists the signal connections for the downsizer module.

Table 3.44. Downsizer interface signals

Signal

Direction

Description

HCLK

Input

System bus clock. Logic is triggered on the clock rising edge.

HRESETn

Input

Activate low asynchronous reset.

64-bit AHB interface signals, AHB slave

HADDRS[31:0]

Input

Address from the 64-bit AHB.

HBURSTS[2:0]

Input

Burst size information on the 64-bit AHB.

HMASTLOCKS

Input

Indicates that the transfer on the 64-bit AHB is locked.

HPROTS[3:0]

Input

Protection information on the 64-bit AHB.

HRDATAS[63:0]

Output

Read data to the 64-bit bus.

HREADYOUTS

Output

HREADY signal feedback to the 64-bit bus, indicating that the downsizer is ready for next operation.

HREADYS

Input

HREADY signal on the 64-bit AHB bus, indicating start and end of transfer on the 64-bit bus.

HRESPS[2:0]

Output

Response from downsizer module to 64-bit bus.

HSELS

Input

Active HIGH select signal to indicate 32-bit memory range is accessed on the 64-bit AHB.

HSIZES[2:0]

Input

Size of the data on the 64-bit AHB.

HWDATAS[63:0]

Input

Write data from the 64-bit bus.

HWRITES

Input

Indication of write/read operation on the 64-bit AHB.

32-bit AHB interface signals, AHB master

HADDRM[31:0]

Output

Address for the 32-bit AHB.

HBURSTM[2:0]

Output

Burst size information on the 32-bit AHB.

HMASTLOCKM

Output

Indicates that the transfer on the 32-bit AHB is locked.

HPROTM[3:0]

Output

Protection information on the 32-bit AHB.

HRDATAM[31:0]

Input

Data read back from AHB slaves.

HREADYM

Output

HREADY feedback to all slaves on the 32-bit AHB.

HREADYOUTM

Input

HREADY from 32-bit AHB slaves or slave multiplexor.

HRESPM[2:0]

Input

HRESP from 32-bit AHB slaves or slave multiplexor.

HSELM

Output

Active HIGH select signal to indicate that a 32-bit bus is accessed. This signal can be used to drive a single AHB slave directly, or drive a secondary AHB decoder if multiple 32-bit AHB slaves are used.

HSIZEM[2:0]

Output

Size of the data on the 32-bit AHB.

HWDATAM[31:0]

Output

Write data to 32-bit AHB slaves.

HWRITEM

Output

Indication of write/read operation on the 32-bit AHB.

Instead of reading HREADY from the 64-bit bus or HREADYOUT from the 32-bit slave multiplexor, the AHB slaves on the 32-bit bus must read the HREADYM generated from the downsizer module. This signal is multiplexed between HREADYOUTM, when a slave attached to the M port of the downsizer is selected, including during 64-bit to 32-bit conversion, and HREADYS, when the downsizer is not selected.

During a conversion, the 64-bit transfer is split into two 32-bit transfers and all the AHB slaves on the 32-bit AHB bus are able to read the HREADY signal generated by the activated 32-bit slave. However, this HREADY signal must not be passed onto HREADY in the 64-bit bus system because this requires the insertion of wait states for the second 32-bit AHB transfer. Because of this, an additional HREADYM signal enables the AHB slave to determine when the end of an AHB transfer has occurred.

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