ARM Cortex-A15 MPCore Processor Technical Reference Manual

Functional DescriptionFigure 2-3 shows a timing example of ACLKENS that changes the CLK toACLKS frequency ratio from 3:1 to 1:1.1 CLKcycle1 CLKcycleCLKACLKENSACLKENS asserts one CLK cyclebefore the rising edge of ACLKSACLKSCLK:ACLKS = 3:1 CLK:ACLKS = 1:1Figure 2-3 ACLKENS with CLK:ACLKS ratio changing from 3:1 to 1:1NoteFigure 2-3 shows the timing relationship between the ACP clock, ACLKS andACLKENS, where ACLKENS asserts one CLK cycle before the rising edge ofACLKS. It is important that the relationship between ACLKS and ACLKENSis maintained.PCLKENDBGThe Debug APB interface is an asynchronous interface that can operate at anyinteger multiple that is equal to or slower than the APB clock, PCLKDBG, usingthe PCLKENDBG signal. For example, the PCLKDBG to internal PCLKDBGfrequency ratio can be 1:1, 2:1, or 3:1. PCLKENDBG asserts one PCLKDBGcycle before the rising edge of the internal PCLKDBG. The PCLKDBG tointernal PCLKDBG frequency ratio can be changed dynamically usingPCLKENDBG.Figure 2-4 shows a timing example of PCLKENDBG that changes thePCLKDBG to internal PCLKDBG frequency ratio from 2:1 to 1:1.1 PCLKDBGcycle1 PCLKDBGcyclePCLKDBGPCLKENDBGinternalPCLKDBGPCLKENDBG asserts one PCLKDBG cyclebefore the rising edge of internal PCLKDBGPCLKDBG:internal PCLKDBG = 2:1 PCLKDBG:internal PCLKDBG = 1:1Figure 2-4 PCLKENDBG with PCLKDBG:internal PCLKDBG ratio changing from 2:1 to 1:1ATCLKEN The ATB interface is a synchronous interface that can operate at any integermultiple that is slower than the main processor clock, CLK, using theATCLKEN signal. For example, the CLK to ATCLK frequency ratio can be 2:1,3:1, or 4:1, where ATCLK is the ATB bus clock. ATCLKEN asserts three CLKcycles before the rising edge of ATCLK. Three CLK cycles are required topermit propagation delay from the ATCLKEN input to the processor. The CLKto ATCLK frequency ratio can be changed dynamically using ATCLKEN.ARM DDI 0438I Copyright © 2011-2013 ARM. All rights reserved. 2-9ID062913Non-Confidential