Cypress CY7C68013A manual Single and Burst Synchronous Write

								CY7C68013A, CY7C68014A
								CY7C68015A, CY7C68016A
10.17.2	Single and Burst Synchronous Write
	Figure 31. Slave FIFO Synchronous Write Sequence and Timing Diagram[20]
		tIFCLK
IFCLK
	tSFA		t		tSFA						t
			FAH								FAH
FIFOADR
	t=0	tSWR	t	T=0	>= t	SWR					>= tWRH
			WRH
SLWR
	t=2		t=3		T=2						T=5
SLCS
			tXFLG								tXFLG
FLAGS
		tSFD	tFDH		tSFD		tFDH	tSFD tFDH		tSFD	tFDH
DATA		N				N+1		N+2		N+3
	t=1				T=1		T=3		T=4	tSPE	tPEH

PKTEND

The Figure 31 shows the timing relationship of the SLAVE FIFO signals during a synchronous write using IFCLK as the synchro- nizing clock. The diagram illustrates a single write followed by burst write of 3 bytes and committing all 4 bytes as a short packet using the PKTEND pin.

■At t = 0 the FIFO address is stable and the signal SLCS is asserted. (SLCS may be tied low in some applications) Note that tSFA has a minimum of 25 ns. This means when IFCLK is running at 48 MHz, the FIFO address setup time is more than one IFCLK cycle.

■At t = 1, the external master/peripheral must outputs the data value onto the data bus with a minimum set up time of tSFD before the rising edge of IFCLK.

■At t = 2, SLWR is asserted. The SLWR must meet the setup time of tSWR (time from asserting the SLWR signal to the rising edge of IFCLK) and maintain a minimum hold time of tWRH (time from the IFCLK edge to the deassertion of the SLWR signal). If the SLCS signal is used, it must be asserted with SLWR or before SLWR is asserted (The SLCS and SLWR signals must both be asserted to start a valid write condition).

■While the SLWR is asserted, data is written to the FIFO and on the rising edge of the IFCLK, the FIFO pointer is incremented. The FIFO flag is also updated after a delay of tXFLG from the rising edge of the clock.

The same sequence of events are also shown for a burst write and are marked with the time indicators of T = 0 through 5.

Note For the burst mode, SLWR and SLCS are left asserted for the entire duration of writing all the required data values. In this burst write mode, after the SLWR is asserted, the data on the

FIFO data bus is written to the FIFO on every rising edge of IFCLK. The FIFO pointer is updated on each rising edge of IFCLK. In Figure 31, after the four bytes are written to the FIFO, SLWR is deasserted. The short 4 byte packet can be committed to the host by asserting the PKTEND signal.

There is no specific timing requirement that should be met for asserting PKTEND signal with regards to asserting the SLWR signal. PKTEND can be asserted with the last data value or thereafter. The only requirement is that the setup time tSPE and the hold time tPEH must be met. In the scenario of Figure 31, the number of data values committed includes the last value written to the FIFO. In this example, both the data value and the PKTEND signal are clocked on the same rising edge of IFCLK. PKTEND can also be asserted in subsequent clock cycles. The FIFOADDR lines should be held constant during the PKTEND assertion.

Although there are no specific timing requirement for the PKTEND assertion, there is a specific corner case condition that needs attention while using the PKTEND to commit a one byte/word packet. Additional timing requirements exists when the FIFO is configured to operate in auto mode and it is desired to send two packets: a full packet (full defined as the number of bytes in the FIFO meeting the level set in AUTOINLEN register) committed automatically followed by a short one byte or word packet committed manually using the PKTEND pin.

In this case, the external master must ensure to assert the PKTEND pin at least one clock cycle after the rising edge that caused the last byte or word that needs to be clocked into the previous auto committed packet (the packet with the number of bytes equal to what is set in the AUTOINLEN register). Refer to Figure 23 for further details on this timing.

Document #: 38-08032 Rev. *L Page 51 of 62

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