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Electrical Specifications
132
April 2001 Revised October 2005
SPRS174M
6.27
External Interface Ready-on-Write Timing With One External Wait State
Table 637. External Memory Interface Write Switching Characteristics (Ready-on-Write, 1 Wait State)
PARAMETER
MIN
MAX
UNIT
td(XCOH-XZCSL)
Delay time, XCLKOUT high to zone chip-select active low
1
ns
td(XCOHL-XZCSH)
Delay time, XCLKOUT high or low to zone chip-select inactive high
2
3
ns
td(XCOH-XA)
Delay time, XCLKOUT high to address valid
2
ns
td(XCOHL-XWEL)
Delay time, XCLKOUT high/low to XWE low
2
ns
td(XCOHL-XWEH)
Delay time, XCLKOUT high/low to XWE high
2
ns
td(XCOH-XRNWL)
Delay time, XCLKOUT high to XR/W low
1
ns
td(XCOHL-XRNWH)
Delay time, XCLKOUT high/low to XR/W high
2
1
ns
ten(XD)XWEL
Enable time, data bus driven from XWE low
0
ns
td(XWEL-XD)
Delay time, data valid after XWE active low
4
ns
th(XA)XZCSH
Hold time, address valid after zone chip-select inactive high
ns
th(XD)XWE
Hold time, write data valid after XWE inactive high
TW2
ns
tdis(XD)XRNW
Maximum time for DSP to release the data bus after XR/W inactive high
4
ns
During inactive cycles, the XINTF address bus will always hold the last address put out on the bus. This includes alignment cycles.
TW = trail period, write access (see Table 628)
Table 638. Synchronous XREADY Timing Requirements (Ready-on-Write, 1 Wait State)§
MIN
MAX
UNIT
tsu(XRDYsynchL)XCOHL
Setup time, XREADY (synchronous) low before XCLKOUT high/low
15
ns
th(XRDYsynchL)
Hold time, XREADY (synchronous) low
12
ns
te(XRDYsynchH)
Earliest time XREADY (synchronous) can go high before the sampling XCLKOUT
edge
3
ns
tsu(XRDYsynchH)XCOHL
Setup time, XREADY (synchronous) high before XCLKOUT high/low
15
ns
th(XRDYsynchH)XZCSH
Hold time, XREADY (synchronous) held high after zone chip select high
0
ns
§ The first XREADY (synchronous) sample occurs with respect to E in Figure 634:
E =(XWRLEAD + XWRACTIVE) tc(XTIM)
When first sampled, if XREADY (synchronous) is found to be high, then the access will complete. If XREADY (synchronous) is found to be low,
it will be sampled again each tc(XTIM) until it is found to be high.
For each sample, setup time from the beginning of the access can be calculated as:
D =(XWRLEAD + XWRACTIVE +n 1) tc(XTIM) tsu(XRDYsynchL)XCOHL
where n is the sample number: n = 1, 2, 3, and so forth.
Table 639. Asynchronous XREADY Timing Requirements (Ready-on-Write, 1 Wait State)
MIN
MAX
UNIT
tsu(XRDYasynchL)XCOHL
Setup time, XREADY (asynchronous) low before XCLKOUT high/low
11
ns
th(XRDYasynchL)
Hold time, XREADY (asynchronous) low
8
ns
te(XRDYasynchH)
Earliest time XREADY (asynchronous) can go high before the sampling
XCLKOUT edge
3
ns
tsu(XRDYasynchH)XCOHL
Setup time, XREADY (asynchronous) high before XCLKOUT high/low
11
ns
th(XRDYasynchH)XZCSH
Hold time, XREADY (asynchronous) held high after zone chip select high
0
ns
The first XREADY (synchronous) sample occurs with respect to E in Figure 635:
E = (XWRLEAD + XWRACTIVE 2) tc(XTIM)
When first sampled, if XREADY (asynchronous) is found to be high, then the access will complete. If XREADY (asynchronous) is found to be
low, it will be sampled again each tc(XTIM) until it is found to be high.
For each sample, setup time from the beginning of the access can be calculated as:
D = (XWRLEAD + XWRACTIVE 3 + n) tc(XTIM) tsu(XRDYasynchL)XCOHL
where n is the sample number: n = 1, 2, 3, and so forth.