TP3420AV National Semiconductor, TP3420AV Datasheet - Page 29

• Manufacturer Part Number: TP3420AV
• Manufacturer: National Semiconductor

Specifications of TP3420AV

• Number Of Line Interfaces: 1
• Control Interface: HDLC
• Package Type: PLCC
• Lead Free Status / Rohs Status: Not Compliant

0 (MFC INT)
5
10
15
20
25
0 (MFC INT)
5
10
15
20
25
SC1 Messaging Sequence
is checked to see if it contains new data; if yes the data is
sent out from the MFT1H FIFO, if not, then the data from the
MFT1L register is sent.
If both the buffers are full, then a third load to the MFT1H
register will cause the first buffer to be overwritten by the
second and the second buffer to be loaded with the third
load. This way if a DTSE and FECV are already loaded, and
the power on the NT1 starts to fail, the software can still write
a LP command in the MFT1H register as well as the MFT1L
register. This ensures that the commands will be sent out at
the earliest moment and will continue until the power is com-
pletely lost.
Whenever a MFT1H command is written, a software flag
FL__EXT (extend SC1L) should be set. This flag informs the
software that 1 occurrence of the present 6x repetition of the
SC1L messages was overwritten by a message from SC1H,
and hence it is necessary to extend the MFT1L command for
another 30 ms to guarantee 6x tranmission. This flag is reset
after the next 30 ms tick.
10
15
20
25
0 (MFC INT)
5
Time
(ms)
I430 Frame Content
(DTSE)
(FECV)
(DTSE)
(FECV)
(IDLE)
(IDLE)
(IDLE)
(IDLE)
(IDLE)
(IDLE)
(LRS)
(LRS)
(LRS)
(LRS)
(LRS)
(LRS)
(LRS)
(LRS)
SC1
if FL__EXT flag not set, check for new flags on SC1L, assume LRS.
Check for SC2 channel. Send SC2 command
SC1__NB(IDLE)
SC1__NB(LRS)
if FL__EXT flag not set, check for new flags on SC1L, assume IDLE.
Check for SC2 channel Flags. Send SC2 command as appropriate.
SC1__NB(LRS)
SC1__NB
Assume DTSE-IN Interrupt from UID, Send DTSE
Set the FL__EXT. SC1L__PB
RMFE in Interrupt from local SID, FECV
SC1L__PB
if FL__EXT flag set, do not check for new flags on SC1L, but check for
SC2 channel. Reset FL__EXT. Send SC2 command as appropriate,
SC1L__NB (IDLE)
DTSE-IN Interrupt from UID, DTSE
FL__EXT, SC1L__PB
Also RMFE in Interrupt from local SID, FECV
FL__EXT. SC1L__PB
Now the FECV command is queued in the MFT1H register.
29
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Example
Assume Software flags and buffers are defined as:
SC1L__PB - software variable, indicating previous data sent
via the SC1L channel
SC1L__NB - software variable, indicating the next value to
be sent via the SC1L channel
FL__EXT - Flag to Extend SC1L command for another 30
ms.
MFT1L, MFT1H and MFT2, are the device registers.
The sequences of events shown below indicate activity on
the SC1 channel on the line and the actions required by the
local microcontroller at each 30 ms (MFC status interrupt)
ticks.
MFT1L(IDLE).
MFT1L(LRS). Set FL-EXT.
>
>
>
SC1__PB, SC1L command(IDLE)
SC1__PD, SC1 command(LRS)
MFT1L.
>
MFT1L.
>
>
MFT1L register.
MFT1L register.
Actions Required
>
MFT1L (LRS).
>
MFT1H register. Set
>
MFT1H,
>
>
MFT1H register. Set
MFT2.
>
>
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MFT1H register.
SC1__NB,
SC1__NB,
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