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4 questions on the above standard.
==================================
Any answers - I'm particularly interested in the correct interpretation of the
standard as opposed to what devices actually do - developing a tester for
checking conformity.
Note: paragraph 3.2.1 - Precedence
states that figures take precedence over text (and tables over both),
so I take the state diagram descriptions as taking precedence over
any implied functionality in the text.
_____________________
Figure 15, page 229 of the above standard (Device power-on or hardware reset
state diagram) states that PDIAG- is only Asserted or Negated ON transition
D1HR1:DI2 (exc. whatever it's state may have been in DHR0: RESET).
However, table in Figure 21, page 241 (Device bus idle state diagram) states
that PDIAG- is always Released.
So, if transitions are instantaneous (last paragraph, section 3.2.7 , P8) how
in reality can PDIAG- be ever anything but Released.
It seems device 0 must Assert or Negate PDIAG- until at least device 0 has
had the opportunity to sample it (D0HR2:Sample_PDIAG-).
(Note: same for Figure 39, page 277 Device 1 EXECUTE DEVICE DIAGNOSTIC
command state diagram - D1ED2:DI2 transition).
Q1: When should Device 1 Release PDIAG- after D1HR1:DI2 (D1ED2:DI2) and
where is this stated?
________
In a similar vein, DASP- is Asserted only whilst device 1 is in
D1HR1:Set_status. Once finished and off idling (DI2), DASP- is Released (=
Negated with 10K Pull Up [p11 4.2.1]) according to table in Figure 21.
Meanwhile, device 0 passes to State D0HR1:Sample_DASP- . If Device 1
diagnostic is extremely quick (< 1ms), Device 1 will already be in DI2
before Device 0 has reached D0HR1. Device 1 must Assert DASP- until at least
device 0 has had the opportunity to sample it (D0HR1:Sample_DASP-).
Q2: When should Device 1 Release DASP- after D1HR0 and where is this stated?
_ _ _ _
I thought that DASP- Assert is a function of device 1 only (device 0 always
keeps it released).
Q3: When would Device 0 ever Assert or Release DASP-?
- Implied by description of the function of D0HR0,
or is this catering for a device designation switch?!
(Was device 1, now device 0 - think not!)
- Alternatively, is it time allowance for the OTHER device (device 1)
to release DASP- (D0HR0)? Why - device 1 is only going to re-assert
it?
- Or is it time allowance for the devices to settle down after power
application/reset?
_ _ _ _
Q4.1: Is there a scenerio where the host ever samples DASP-?
The cable definitions don't exclude it from reaching the host, but I
haven't as yet detected a description of the host actually using it in the
standard. I may have missed it!
Q4.2 Can at least one instance in the standard (section number) be identified
which describes the host using DASP-?
Q4.3 Should DASP- be asserted by device 1 all/most of the time (to
represent its presence)?
Thanks in advance
Keith
--
Keith Clausen, STMicroelectronics,
Mail: 1000 Aztec West, Bristol BS32 4SQ, UK
Email: [EMAIL PROTECTED]
Phone: +44 1454 462457 Fax: +44 1454 617910
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