Cypress CY7C1380F, CY7C1380D manual Functional Overview, Single Write Accesses Initiated by Adsp

CY7C1380D, CY7C1382D CY7C1380F, CY7C1382F

Functional Overview

All synchronous inputs pass through input registers controlled by the rising edge of the clock. All data outputs pass through output registers controlled by the rising edge of the clock. Maximum access delay from the clock rise (tCO) is 2.6 ns (250 MHz device).

The CY7C1380D/CY7C1382D/CY7C1380F/CY7C1382F supports secondary cache in systems using a linear or inter- leaved burst sequence. The interleaved burst order supports Pentium and i486™ processors. The linear burst sequence suits processors that use a linear burst sequence. The burst order is user selectable, and is determined by sampling the MODE input. Accesses can be initiated with either the processor address strobe (ADSP) or the controller address strobe (ADSC). Address advancement through the burst sequence is controlled by the ADV input. A two-bit on-chip wraparound burst counter captures the first address in a burst sequence and automatically incre- ments the address for the rest of the burst access.

Byte write operations are qualified with the byte write enable (BWE) and byte write select (BWX) inputs. A global write enable (GW) overrides all byte write inputs and writes data to all four bytes. All writes are simplified with on-chip synchronous self-timed write circuitry.

Three synchronous chip selects (CE1, CE2, CE3) and an asynchronous output enable (OE) provide for easy bank selection and output tri-state control. ADSP is ignored if CE1 is HIGH.

Single Write Accesses Initiated by ADSP

This access is initiated when both the following conditions are satisfied at clock rise: (1) ADSP is asserted LOW and (2) CE1, CE2, and CE3 are all asserted active. The address presented to A is loaded into the address register and the address advancement logic while being delivered to the memory array. The write signals (GW, BWE, and BWX) and ADV inputs are ignored during this first cycle.

ADSP triggered write accesses require two clock cycles to complete. If GW is asserted LOW on the second clock rise, the data presented to the DQs inputs is written into the corre- sponding address location in the memory array. If GW is HIGH, then the write operation is controlled by BWE and BWX signals.

The CY7C1380D/CY7C1382D/CY7C1380F/CY7C1382F provides byte write capability that is described in the write cycle descriptions table. Asserting the byte write enable input (BWE) with the selected byte write (BWX) input, selectively writes to only the desired bytes. Bytes not selected during a byte write operation remain unaltered. A synchronous self-timed write mechanism has been provided to simplify the write operations.

The CY7C1380D/CY7C1382D/CY7C1380F/CY7C1382F is a common I/O device, the output enable (OE) must be deserted HIGH before presenting data to the DQs inputs. Doing so tri-states the output drivers. As a safety precaution, DQs are automatically tri-stated whenever a write cycle is detected, regardless of the state of OE.

Single Read Accesses

This access is initiated when the following conditions are satisfied at clock rise: (1) ADSP or ADSC is asserted LOW,

(2)CE1, CE2, CE3 are all asserted active, and (3) the write signals (GW, BWE) are all deserted HIGH. ADSP is ignored if

CE1 is HIGH. The address presented to the address inputs (A) is stored into the address advancement logic and the address register while being presented to the memory array. The corre- sponding data is enabled to propagate to the input of the output registers. At the rising edge of the next clock, the data is enabled to propagate through the output register and onto the data bus within 2.6 ns (250 MHz device) if OE is active LOW. The only exception occurs when the SRAM is emerging from a deselected state to a selected state; its outputs are always tri-stated during the first cycle of the access. After the first cycle of the access, the outputs are controlled by the OE signal. Consecutive single read cycles are supported. Once the SRAM is deselected at clock rise by the chip select and either ADSP or ADSC signals, its output tri-states immediately.

Single Write Accesses Initiated by ADSC

ADSC write accesses are initiated when the following conditions are satisfied: (1) ADSC is asserted LOW, (2) ADSP is deserted HIGH, (3) CE1, CE2, and CE3 are all asserted active, and (4) the appropriate combination of the write inputs (GW, BWE, and BWX) are asserted active to conduct a write to the desired byte(s). ADSC-triggered Write accesses require a single clock cycle to complete. The address presented to A is loaded into the address register and the address advancement logic while being delivered to the memory array. The ADV input is ignored during this cycle. If a global write is conducted, the data presented to the DQs is written into the corresponding address location in the memory core. If a byte write is conducted, only the selected bytes are written. Bytes not selected during a byte write operation remain unaltered. A synchronous self-timed write mechanism has been provided to simplify the write operations.

The CY7C1380D/CY7C1382D/CY7C1380F/CY7C1382F is a common I/O device, the output enable (OE) must be deserted HIGH before presenting data to the DQs inputs. Doing so tri-states the output drivers. As a safety precaution, DQs are automatically tri-stated whenever a write cycle is detected, regardless of the state of OE.

Document #: 38-05543 Rev. *F Page 8 of 34

[+] Feedback