CY7C0850AV/CY7C0851AV
CY7C0852AV/CY7C0853AV
Document #: 38-06070 Rev. *G
Page 7 of 31
Master Reset
The FLEx36 family devices undergo a complete reset by
taking its MRST input LOW. The MRST input can switch
asynchronously to the clocks. The MRST initializes the
internal burst counters to zero, and the counter mask registers
to all ones (completely unmasked). The MRST also forces the
Mailbox Interrupt (INT) flags and the Counter Interrupt
(CNTINT) flags HIGH. The MRST must be performed on the
FLEx36 family devices after power-up.
Mailbox Interrupts
The upper two memory locations may be used for message
passing and permit communications between ports. Table 2
shows the interrupt operation for both ports of CY7C0853AV.
The highest memory location, 3FFFF is the mailbox for the
right port and 3FFFE is the mailbox for the left port. Table 2
shows that in order to set the INTR flag, a Write operation by
the left port to address 3FFFF will assert INTR LOW. At least
one byte has to be active for a Write to generate an interrupt.
A valid Read of the 3FFFF location by the right port will reset
INTR HIGH. At least one byte has to be active in order for a
Read to reset the interrupt. When one port Writes to the other
port’s mailbox, the INT of the port that the mailbox belongs to
is asserted LOW. The INT is reset when the owner (port) of the
mailbox Reads the contents of the mailbox. The interrupt flag
is set in a flow-thru mode (i.e., it follows the clock edge of the
writing port). Also, the flag is reset in a flow-thru mode (i.e., it
follows the clock edge of the reading port).
Each port can read the other port’s mailbox without resetting
the interrupt. And each port can write to its own mailbox
without setting the interrupt. If an application does not require
message passing, INT pins should be left open.
Table 2. Interrupt Operation Example[1, 4, 5, 6, 7]
Function
Left Port
Right Port
R/WL
CEL
A0L–17L
INTL
R/WR
CER
A0R–17R
INTR
Set Right INTR Flag
L
L
3FFFF
X
X
X
X
L
Reset Right INTR Flag
X
X
X
X
H
L
3FFFF
H
Set Left INTL Flag
X
X
X
L
L
L
3FFFE
X
Reset Left INTL Flag
H
L
3FFFE
H
X
X
X
X
Table 3. Address Counter and Counter-Mask Register Control Operation (Any Port)[8, 9]
CLK
MRST CNT/MSK
CNTRST
ADS
CNTEN
Operation
Description
X
L
X
X
X
X
Master Reset
Reset address counter to all 0s and mask
register to all 1s.
H
H
L
X
X
Counter Reset
Reset counter unmasked portion to all 0s.
H
H
H
L
L
Counter Load
Load counter with external address value
presented on address lines.
H
H
H
L
H
Counter Readback Read out counter internal value on address
lines.
H
H
H
H
L
Counter Increment Internally increment address counter value.
H
H
H
H
H
Counter Hold
Constantly hold the address value for
multiple clock cycles.
H
L
L
X
X
Mask Reset
Reset mask register to all 1s.
H
L
H
L
L
Mask Load
Load mask register with value presented on
the address lines.
H
L
H
L
H
Mask Readback
Read out mask register value on address
lines.
H
L
H
H
X
Reserved
Operation undefined
Notes:
4. CE is internal signal. CE = LOW if CE0 = LOW and CE1 = HIGH. For a single Read operation, CE only needs to be asserted once at the rising edge of the CLK
and can be deasserted after that. Data will be out after the following CLK edge and will be three-stated after the next CLK edge.
5. OE is “Don’t Care” for mailbox operation.
6. At least one of B0, B1, B2, or B3 must be LOW.
7. A16x is a NC for CY7C0851AV, therefore the Interrupt Addresses are FFFF and EFFF; A16x and A15x are NC for CY7C0850AV, therefore the Interrupt Addresses
are 7FFF and 6FFF.
8. “X” = “Don’t Care,” “H” = HIGH, “L” = LOW.
9. Counter operation and mask register operation is independent of chip enables.
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