A.1 AHB-Lite slave interface signals

The AHB-Lite slave interface processes several input and output AHB-Lite signals.

The following table shows the signals that are used by the AHB-Lite slave interface.

Table A-1 AHB-Lite slave interface signals

Signal name Direction Source or destination Description
hsel Input Decoder

Slave select signal.

Indicates that the current transfer is intended for the Flash controller.

haddr[21:0] Input AHB master

Address bus.

22 bits wide. Allows a 4MB address space to be split into a 2MB main and a 2MB extended memory area. MSB haddr[21] specifies the selection between the two areas:

0 = Main area.

1 = Extended area.

htrans[1:0] Input AHB master

Indicates the current transfer type:

0b00 = IDLE.

0b01 = BUSY.

0b10 = NONSEQUENTIAL.

0b11 = SEQUENTIAL.

hwrite Input AHB master

Read‑only.

Only reads are allowed. Can be tied LOW externally.

Writes generate an error.

hsize[2:0] Input AHB master

Indicates the size of access:

0b000 = Byte.

0b001 = Halfword.

0b010 = Word.

0b011 = Doubleword.

0b100 = 4-word line.

0b101 = 8-word line.

0b110 = 512-bit width.

0b111 = 1024-bit width.

Only 0b100 is allowed. Other access sizes generate an error.

hburst[2:0] Input AHB master

Indicates if the transfer is part of the burst:

0b000 = Single.

0b001 = Incr.

0b010 = Wrap4.

0b011 = Incr4.

0b100 = Wrap8.

0b101 = Incr8.

0b110 = Wrap16.

0b111 = Incr16.

hmastlock Input AHB master

Indicates that the transaction on the bus must be atomic.

Used for blocking arbitration over the GFB.

hready Input Multiplexer or AHB master

When HIGH, indicates that a bus transfer has completed.

To extend a transfer, drive this signal LOW.

hreadyout Output Multiplexer or AHB master

When HIGH, indicates that a bus transfer has completed.

To extend a transfer, drive this signal LOW.

Isolation and reset value = 0b1.

hresp Output Multiplexer or AHB master

Transfer response status:

0b0 = OKAY.

0b1 = ERROR.

Isolation and reset value = 0b0.

hrdata[127:0] Output Multiplexer or AHB master

Read data.

Isolation and reset value = 0x0.

Note:

AHB-Lite signals that are not shown in the table are not used in GFC-100.
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