CY7C43644
CY7C43664
CY7C43684
Document #: 38-06022 Rev. *B
Page 10 of 39
When reading data from FIFO1 in the byte or word format, the
unused B0–35 outputs are indeterminate.
Bus-Matching FIFO2 Writes
Data is written to the FIFO2 RAM in 36-bit long-word incre-
ments. Data written to FIFO2 with a byte or word bus size
stores the initial bytes or words in auxiliary registers. The
CLKB rising edge that writes the fourth byte or the second
word of the long-word to FIFO2 also stores the entire
long-word in FIFO2 RAM.
When reading data from FIFO2 in byte or word format, the
unused B0–35 outputs are LOW.
Retransmit (RT1, RT2)
The retransmit feature is beneficial when transferring packets
of data. It enables the receipt of data to be acknowledged by
the receiver and retransmitted if necessary. Retransmit
function applies to CY standard mode only.
The number of 36-/18-/9-bit words written into the FIFO should
be less than full depth minus 2/4/8 words between the reset of
the FIFO (master or partial) and Retransmit setup. A LOW
pulse on RT1, (RT2) resets the internal read pointer to the first
physical location of the FIFO. CLKA and CLKB may be free
running but ENB, (ENA) must be disabled during and tRTR
after the retransmit pulse. With every valid read cycle after
retransmit, previously accessed data is read and the read
pointer is incremented until it is equal to the write pointer. Flags
are governed by the relative locations of the read and write
pointers and are updated during a retransmit cycle. Data
written to the FIFO after activation of RT1, (RT2) are trans-
mitted also. The full depth of the FIFO can be repeatedly
retransmitted.
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