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HELP: Timing about AHB hready

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hiky

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ahb timing

In AHB, when the master change slaves, for example,from slave0 to slave1,the slave 1 must use the global ready at the transfer begining to check weather the last data form slave0 have transfered success. am i right?
but the hreadg(global hready) is generated form all the hreay form several slaves by combination logic, so the hreadg is from slaves , through arbiter ,and turn back to slaves, the timing of the path which included this arc is too bad , and the AHB performance are not satisfied!!
is there any method to resolve this problem??
help!!!!!
 

amba ahb problem of overlapping masters

hi
ahb slave's input doesn't has hready signal, it output that signal, and the slave which output hready signal and arbiter take action depend on the signal(if the slave is selected)
 

ahb hready slave

thanks for your reply, but i am readlly confused about How the current slave know the data transfer belong to the previous slave have been done if the slave don't care the global hready signal? can U tell me ?
 

ahb hready signal

it is just like sever-client architechture, ahb is the sever, apb is the client.
 

ahb hready

It is control by the arbiter.see if master want to communicate with other slave then arbiter will monitor whether hready for the data has been received or not once it gets high then only arbiter ll alow the access to other master.
in other case if same master want to communicatewith other slave it control/address signal will never propagate untill it will receive hready high and after that decoder logic of AHB will deceide where it has to send the current data.
For more detail go through the AHB doc.
 

ahb slave hready signal

thanks alam, but i have a question about slave change, how does the master know weather the slave is being to change or not? the slave is selected by hsel generated by address decoder, and the decoder is inside arbiter , the master does not see the select signal at all. Is there a method that slave not have to use hreadg(global hready singal) to judge the previous slave's transaction?
 

ahb hready question

master know which slave is slected by slave to master multiplexer.when hsel change, if the last slave's hready is low, so the arbiter will'not let the current slave(has coming into addr phase) come into data phase .
 

slave input hready signal

Sorry, phoenixfeng, i can't get your point, how the arbiter control the slave not coming into data phase? by generating 'hsel' signal or any other signal ? can you give me some more detail information? thanks a lot!!

can the slave not have to see the hreadyg signal ?
 

ahb signals hsel

hi,hiky
the slave need to see its own hready signal, it doesn't have hready input signal but output only.
when slave changing, imagining that last slave is slave0,and its master is master0, the current slave is slave1, and its master is master1.During the last cycle of slave0, if its hready signal is active, then the grant1 is active, and master1 comes into addr phase. Because AMBA is pipeline architecture, the last data phase of slave0 is overlapped with the addr phase of slave1. During this phase, the slave to master MUX select slave1, the rdata signal of slave0 is connected to all masters. Now, master0 is at data phase, so it gets the data.But master1 is at addr phase, so it does noting with the rdata. If the hready signal of slave0 is active at this phase, master1 see this signal and comes into data phase, if not master1 stays at addr phase.At the same time ,if arbiter see hready active, it let the S2M MUX select slave1.
Slave needn't to focus on whether the last transfer has completed or not when grant changing. It just generates its own signal depend on control signal. The last transfer may be not completed, but slave1's output will not be selected by S2M Mux
so it need not much care.

Keep in mind that AMBA is made up of master, slave, and infrastructure(arbiter, decoder, M2S mux, and S2M mux), everyone does different jobs and works together.

In a word, the slave generates hready signal, not only the slave see its own signal, but also the master and arbiter do the some work.
Just for a reference.
 

address phase in ahb

phoenixfeng said:
hi,hiky
the slave need to see its own hready signal, it doesn't have hready input signal but output only.
when slave changing, imagining that last slave is slave0,and its master is master0, the current slave is slave1, and its master is master1.During the last cycle of slave0, if its hready signal is active, then the grant1 is active, and master1 comes into addr phase. Because AMBA is pipeline architecture, the last data phase of slave0 is overlapped with the addr phase of slave1. During this phase, the slave to master MUX select slave1, the rdata signal of slave0 is connected to all masters. Now, master0 is at data phase, so it gets the data.But master1 is at addr phase, so it does noting with the rdata. If the hready signal of slave0 is active at this phase, master1 see this signal and comes into data phase, if not master1 stays at addr phase.At the same time ,if arbiter see hready active, it let the S2M MUX select slave1.
Slave needn't to focus on whether the last transfer has completed or not when grant changing. It just generates its own signal depend on control signal. The last transfer may be not completed, but slave1's output will not be selected by S2M Mux
so it need not much care.

Keep in mind that AMBA is made up of master, slave, and infrastructure(arbiter, decoder, M2S mux, and S2M mux), everyone does different jobs and works together.

In a word, the slave generates hready signal, not only the slave see its own signal, but also the master and arbiter do the some work.
Just for a reference.
Click to expand...


sorry ,you are wrong for this explaintion.

"An AHB slave must have the HREADY signal as both an input and an output.

HREADY is required as an output from a slave so that the slave can extend the data phase of a transfer.

HREADY is also required as an input so that the slave can determine when the previously selected slave has completed its final transfer and the first data phase transfer for this slave is about to commence.

Each AHB Slave should have an HREADY output signal (conventionally named HREADYOUT) which is connected to the Slave-to-Master Multiplexer. The output of this multiplexer is the global HREADY signal which is routed to all masters on the AHB and is also fed back to all slaves as the HREADY input.
"

this is right!!!
 

ahb mux vs or

Hi All,

Please reffer forllowing attachment for more clearification.

An AHB slave must have the HREADY signal as both an input and an output.

HREADY_OUT is required as an output from a slave so that the slave can extend the data phase of a transfer.

HREADY_IN is also required as an input so that the slave can determine when the previously selected slave has completed its final transfer and the first data phase transfer for this slave is about to commence.

Each AHB Slave should have an HREADY output signal (conventionally named HREADYOUT) which is connected to the Slave-to-Master Multiplexer. The output of this multiplexer is the global HREADY signal which is routed to all masters on the AHB and is also fed back to all slaves as the HREADY input.(See attachment)

I have made AHBLite to Avalone bridge for that i must have to use both HREADY_IN and HREADY_OUT because i connected more then one avalone slave, if only one slave I think no need ot HreadyIn. AHBLite connected with CortexM1 Master.

--
Shtiansh
 

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