A.1. AMBA AHB signals

The VIC module is connected to the AMBA AHB as a bus slave. Table A.1 lists the AHB signals that are used and produced.

Table A.1. AMBA AHB signal descriptions

Name

Type

Source/

destination

Description

HCLK

Input

Clock source

AMBA AHB bus clock. Times all bus transfers. All signal timings are related to the rising edge of HCLK.

HRESETn

Input

Reset controller

AHB bus reset, active LOW.

HADDR[11:2]

Input

Master

System address bus.

HTRANS

Input

Master

Transfer type. This can be NONSEQUENTIAL, SEQUENTIAL, IDLE, or BUSY. You must connect this signal to HTRANS[1] on the AHB interface. HTRANS[0] is not used.

HWRITE

Input

Master

Transfer direction. Indicates a write transfer when HIGH, and a read transfer when LOW.

HSIZE[2:0]

Input

Master

Size of the transfer. This must be a word, 32-bit, for the VIC, HSIZE[2:0] = 0b010.

HPROT

Input

Master

Memory access protection type. This can be User mode (0) or privileged mode (1). You must connect this signal to HPROT[1] on the AHB interface. HPROT[3], HPROT[2] and HPROT[0] are not used.

HWDATA[31:0]

Input

Master

Write data bus. Transfers data from bus master to bus slaves during write operations.

HSELVIC

Input

Decoder

Slave select signal. This is a combinatorial decode of the address bus. It indicates that the current transfer is intended for the selected slave.

HRDATA[31:0]

Output

Slave

Read data bus. Transfers data from bus slaves to bus master during read operations.

HREADYIN

Input

External slave

Transfer done signal, generated by an alternate slave. When HIGH, indicates that a transfer is complete. You can drive it LOW to extend a transfer.

HREADYOUT

Output

Slave

Transfer done signal, generated by the VIC. When HIGH, indicates that a transfer is complete. You can drive it LOW to extend a transfer.

HRESP[1:0]

Output

Slave

Transfer response. This provides additional transfer status information. The response can be OKAY, ERROR, RETRY, or SPLIT. The VIC responds with either OKAY or ERROR.

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