Cypress CY7C0837AV, CY7C0830AV CY7C0831AV, CY7C0832AV CY7C0832BV, CY7C0833AV, Master Reset

CY7C0837AV, CY7C0830AV CY7C0831AV, CY7C0832AV CY7C0832BV, CY7C0833AV

Master Reset

The FLEx18 family devices undergo a complete reset by taking its MRST input LOW. The MRST input can switch asynchro- nously to the clocks. An MRST initializes the internal burst counters to zero, and the counter mask registers to all ones (completely unmasked). MRST also forces the Mailbox Interrupt (INT) flags and the Counter Interrupt (CNTINT) flags HIGH. MRST must be performed on the FLEx18 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 CY7C0833AV. The highest memory location, 7FFFF is the mailbox for the right port and 7FFFE is the mailbox for the left port. Table 2 shows that to set the INTR flag, a Write operation by the left port to address 7FFFF asserts INTR LOW. At least one byte has to be active for a Write to generate an interrupt. A valid Read of the 7FFFF location by the right port resets INTR HIGH. At least one byte must be active 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-through mode (that is, it follows the clock edge of the writing port). Also, the flag is reset in a flow-through mode (that is, 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.

Address Counter and Mask Register Operations [16]

This section describes the features only apply to 512 Kbit,1 Mbit, 2 Mbit, and 4 Mbit devices. It does not apply to 9 Mbit device. Each port of these devices has a programmable burst address counter. The burst counter contains three registers: a counter register, a mask register, and a mirror register.

Table 2. Interrupt Operation Example [2, 12, 13, 14, 15, 17]

The counter register contains the address used to access the RAM array. It is changed only by the Counter Load, Increment, Counter Reset, and by master reset (MRST) operations.

The mask register value affects the Increment and Counter Reset operations by preventing the corresponding bits of the counter register from changing. It also affects the counter interrupt output (CNTINT). The mask register is changed only by the Mask Load and Mask Reset operations and by the MRST. The mask register defines the counting range of the counter register. It divides the counter register into two regions: zero or more ‘0s’ in the most significant bits define the masked region, one or more ‘1s’ in the least significant bits define the unmasked region. Bit 0 may also be ‘0,’ masking the least significant counter bit and causing the counter to increment by two instead of one.

The mirror register is used to reload the counter register on increment operations (see Retransmit on page 8). It always contains the value last loaded into the counter register, and is changed only by the Counter Load, and by the MRST instruc- tions. Table 3 on page 7 summarizes the operation of these registers and the required input control signals. The MRST control signal is asynchronous. All the other control signals in Table 3 on page 7 (CNT/MSK, CNTRST, ADS, CNTEN) are synchronized to the port’s CLK. All these counter and mask operations are independent of the port’s chip enable inputs (CE0 and CE1).

Counter enable (CNTEN) inputs are provided to stall the operation of the address input and use the internal address generated by the internal counter for fast, interleaved memory applications. A port’s burst counter is loaded when the port’s address strobe (ADS) and CNTEN signals are LOW. When the port’s CNTEN is asserted and the ADS is deasserted, the address counter increments on each LOW to HIGH transition of that port’s clock signal. This reads and writes one word from and to each successive address location until CNTEN s deasserted. The counter can address the entire memory array, and loops back to the start. Counter reset (CNTRST) is used to reset the unmasked portion of the burst counter to I/0s. A counter-mask register is used to control the counter wrap.

FUNCTION

LEFT PORT

RIGHT PORT

R/W

L

CEL

A0L–A18L

INTL

R/WR

CER

A0R–A18R

INTR

Set Right

R Flag

L

L

3FFFF

X

X

X

X

L

INT

Reset Right

R Flag

X

X

X

X

H

L

3FFFF

H

INT

Set Left

L Flag

X

X

X

L

L

L

3FFFE

X

INT

Reset Left

L Flag

H

L

3FFFE

H

X

X

X

X

INT

Set Right

R Flag

L

L

3FFFF

X

X

X

X

L

INT

Notes

12.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 is out after the following CLK edge and is three-stated after the next CLK edge.

13.OE is “Don’t Care” for mailbox operation.

14.At least one of BE0, BE1 must be LOW.

15.A18x is a NC for CY7C0832AV/CY7C0832BV, therefore the Interrupt Addresses are 3FFFF and 3FFFE. A18x and A17x are NC for CY7C0831AV, therefore the Interrupt addresses are 1FFFF and 1FFFE; A18x, A17x and A16x are NC for CY7C0830AV, therefore the Interrupt Addresses are FFFF and FFFE;A18x, A17x, A16x and A15x are NC for CY7C0837AV, therefore the Interrupt Addresses are 7FFF and 7FFE.

16.This section describes the CY7C0832AV/CY7C0832BV, CY7C0831AV, CY7C0830AV and CY7C0837AV having 18, 17, 16 and 15 address bits.

17.“X” = “Don’t Care,” “H” = HIGH, “L” = LOW.

Document #: 38-06059 Rev. *S Page 6 of 28

[+] Feedback