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16 www.xilinx.com XAPP169 (v1.0) November 24, 1999
1-800-255-7778
MP3 NG: A Next Generation Consumer Platform
R
CPU Interface
The CPU Interface block performs three functions: protocol conversion, CPU initialization and
address de-multiplexing. Figure 16 shows a block diagram of this block.
The CPU initialization block generates the required timing for the reset signals and drives
configuration information onto bus grant and the interrupts. This configuration information
configures the boot PROM width and enables the CPU timer. After initialization is complete the
block drives the IRDA and audio DAC interrupts out onto the CPU interrupt signals.
The bus state machine converts the signaling on the CPU bus into the format used on the local
IP bus, or if the transaction is to the USB interface, the signaling accepted by the USBN9602.
The FPGA device resources used to implement this block include an estimated 46 CLBs and
the 54 I/O pads listed in Table 1.
Latch
28
Enable
28
DQ
AOUT[31:4]
GNT_IN
RD_OUT_N
WR_OUT_N[3:0]
ACK_IN
REQ_OUT
Bus State
Machine
CPU_CIP_N
CPU_BE_N[3:0]
CPU_ACK_N
CPU_RD_N
CPU_AD[31:0]
CPU_ADDR[3:2]
2
AOUT[3:2]
DIN[31:0]
DOUT[31:0]
CPU_ALE
IR_INT_N
CPU
Initialization
SYS_CLK
CPU_COLDRESET_N
CPU_RESET_N
CPU_BUSGNT_N
CPU_INT_N[3:0]
DAC_INT_N
SYS_CLK
CPU_WR_N
CPU_MASTERCLK
USB_CS_N
USB_RD_N
USB_WR_N
Figure 16: CPU Interface Block Diagram