7721 datasheet(407/577 Pages) RENESAS

407 / 577 page

APPLICATION

7721 Group User’s Manual

16–4

16.1 Memory connection

16.1.2 How to calculate timing

Timings at which data is read or written when connecting a memory and precautions when connecting a

memory are described below.

For timing requirements of the memory and detailed account except limits described below, also refer to

the memory’s Data book etc. When using bus buffers, various logical circuits, etc., be sure to consider the

propagation delay time etc.

(1)

Timing for reading data

When reading data, the external data bus is placed in a floating state, and data is read from the

external memory. This floating state is maintained after the falling edge of the E signal until an

interval of tpzx(E–DLZ/DHZ) has passed after the rising edge of the E signal. Satisfy tsu(DL/DH-E) when inputting

data read from the external memory.

The following are described below:

•Timing for reading data from the flash memory, SRAM, and DRAM

•Calculation formulas for the external memory’s access time, which are for tsu(DL/DH-E) to be satisfied

___

The memory output enable signal (OE) is assumed to be generated from the E signal.

q Timing for reading data from flash memory and SRAM

Fig. 16.1.1 Timing for reading data from flash memory and SRAM

External memory

data output

V1: This applies when the external data bus has a width of 16 bits (BYTE = “L”).

External memory

output enable signal

(Read signal)

External memory

chip select signal

CE, S

V2: If data is output from the external memory before the falling edge of E, there is a possibility that the tail of

address collides wit

h the head of data.

collides wi h the head of

→ Refer to section “(3) Precautions on memory connection.”

V3: If one of the external memory’s specifications is greater than tpzx(E-DLZ/DHZ) , there is a possibility that the tail

→ Refer to section “(3) Precautions on memory connection.”

Address output and Data input

/D8–A15/D15

A16/D0–A23/D7

ten(OE)

Address

tpzx(E-DLZ/DHZ)

tsu(DL/DH-E)

: Specifications of the M37721

(The others are specifications of

external memory.)

ta(OE)

tDF, tdis(OE)

tw(EL)

Data

ten(CE), ten(S)

Address

ta(CE), ta(S)

ta(AD), tsu(A-DL/DH)

Note: tsu(A-DL/DH) : tsu(A-DL) or tsu(A-DH)

tpzx(E-DLZ/DHZ) : tpzx(E-DLZ) or tpzx(E-DHZ)

tsu(DL/DH-E) : tsu(DL-E) or tsu(DH-E)

data

address

7721 Datasheet(PDF) 407 Page - Renesas Technology Corp

7721 Datasheet(HTML) 407 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL