4-Level FSK Modem Data Pump
Page 35 of 50
MX929B PRELIMINARY INFORMATION
Value of µC variable 'STATE' on entry to IRQ routine
START
( IRQ line goes low )
and corresponding MX929B's actions:
0: Symbol Sync pattern being transmitted,
load Frame Sync pattern & T24S task.
1: Frame Sync pattern being transmitted,
load Station ID bytes and TSID task.
2: Station ID Block being transmitted,
load Header Block bytes &THB task.
Read Status Register
3: Header or Intermediate Block being trransmitted
.
load Intermediate or Last Block bytes & TIB or TLB task.
RETURN
( Not MX929B IRQ )
4: Last block being transmitted,
ignore this interrupt.
No
No
IRQ bit = 1 ?
Yes
5: Waiting for end of transmission,
finish on interrupt with IBEMPTY bit set.
BFREE bit = 1 ?
Yes
E
Yes
'STATE' = 5 ?
No
No
Yes
IBEMPTY bit = 1 ?
E
Yes
IBEMPTY bit = 1 ?
No
E
Write 6 bytes Frame Sync
pattern to the Data Buffer
then write a T24S task to
the Command Register
E
Yes
'STATE' = 0 ?
No
Set µC variable 'STATE' to 9
Write 3 Station ID bytes
to the Data Buffer
then write a TSID task to
the Command Register
Yes
Yes
'STATE' = 1 ?
No
RETURN
( Error )
Write 10 Header Block
data bytes to the Data Buffer
then write a THB task to
the Command Register
'STATE' = 2 ?
No
No
'STATE' = 3 ?
Yes
No
Yes
'STATE' = 4 ?
E
Write 12 Intermediate Block
data bytes to the Data Buffer
then write a TIB task to
Write 8 Last Block
data bytes to the Data Buffer
then write a TLB task to
the Command Register
No
Yes
'IBLOCKS' = 0 ?
the Command Register
Decrement µC variable
'IBLOCKS'
Increment µC variable
'STATE'
RETURN
RETURN
Figure 20: Tx Interrupt Service Routine
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