ADSP-21990BBC datasheet(28/50 Pages) AD

28 / 50 page

Rev. A

Page 28 of 50

August 2007

ADSP-21990

External Port Write Cycle Timing

Table 9 and Figure 10 describe external port write operations.

The external port lets systems extend read/write accesses in

three ways: wait states, ACK input, and combined wait states

and ACK. To add waits with ACK, the DSP must see ACK low

at the rising edge of EMI clock. ACK low causes the DSP to wait,

and the DSP requires two EMI clock cycles after ACK goes high

to finish the access. For more information, see the External Port

chapter in the ADSP-2199x Mixed Signal DSP Controller Hard-

ware Reference.

Table 9. External Port Write Cycle Timing

Parameter

Min

Max

Unit

Timing Requirements

1, 2

tAKW

ACK Strobe Pulse Width

12.5

tDWSAK

ACK Delay from XMS Low

0.5tEMICLK – 1

Switching Characteristics

tCSWS

Chip Select Asserted to WR Asserted Delay

0.5tEMICLK – 4

tAWS

Address Valid to WR Setup and Delay

0.5tEMICLK – 3

tWSCS

WR Deasserted to Chip Select Deasserted

0.5tEMICLK – 4

tWSA

WR Deasserted to Address Invalid

0.5tEMICLK – 3

tWW

WR Strobe Pulse Width

tEMICLK–2 + W

tCDA

WR to Data Enable Access Delay

tCDD

WR to Data Disable Access Delay

0.5tEMICLK – 3

0.5tEMICLK + 4

tDSW

Data Valid to WR Deasserted Setup

tEMICLK + 1 + W

tEMICLK + 7 + W

tDHW

WR Deasserted to Data Invalid Hold Time; E_WHC

4, 5

3.4

tDHW

WR Deasserted to Data Invalid Hold Time; E_WHC4, 6

tEMICLK + 3.4

tWWR

WR Deasserted to WR, RD Asserted

tHCLK

1 tEMICLK is the external memory interface clock period. tHCLK is the peripheral clock period.

2 These are timing parameters that are based on worst-case operating conditions.

3 W = (number of wait states specified in wait register)

tBMCLK

4 Write hold cycle–memory select control registers (MS

CTL).

5 Write wait state count (E_WHC) = 0

6 Write wait state count (E_WHC) = 1

ADSP-21990BBC датащи(PDF) 28 Page - Analog Devices

ADSP-21990BBC датащи(HTML) 28 Page - Analog Devices

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

датащи скачать

ссылки URL