Data Sheet

4-Level FSK Modem Data Pump Page 32 of 47 MX919B PRELIMINARY INFORMATION
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.
Ye s
No
RETURN
RETURN
'STATE' = 3 ?
Set µC variable 'STATE' to 9
RETURN
( Error )
E
Decrement µC variable
'IBLOCKS'
Write 8 Last Block
data bytes to the Data Buffer
then write a TLB task to
the Command Register
Write 6 byte Frame Sync
pattern to the Data Buffer
then write a T24S task to
the Command Register
Write 10 Header Block
data bytes to the Data Buffer
then write a THB task to
the Command Register
Increment µC variable
'STATE'
Read Status Register
Ye s
Ye s
No
No
No
Ye s
No
START
( line goes low )IRQ
RETURN
( Not MX919B IRQ )
IRQ bit = 1 ?
BFREE bit = 1 ?
'STATE' = 4 ?
'IBLOCKS' = 0 ?
'STATE' = 1 ?
Ye s
IBEMPTY bit = 1 ?
Ye s
No
'STATE' = 2 ?
No
Ye s
'STATE' = 0 ?
IBEMPTY bit = 1 ?
Write 12 Intermediate Block
data bytes to the Data Buffer
then write a TIB task to
the Command Register
E
No
E
Ye s
E
E
No
No
Ye s
Ye s
Value of C variable 'STATE' on entry to IRQ routine
and corresponding MX919B's actions:
0: Symbol Sync pattern being transmitted,
load Frame Sync pattern & T24S task.
1: Frame Sync pattern being transmitted,
load Header Block bytes and THB task.
2: Header or Intermmediate Block being transmitted,
load Intermediate or Last Block bytes & TIB or TLB task.
3: Last block being transmitted,
ignore this interrupt.
4: Waiting for end of transmission,
finish on interrupt with IBEMPTY bit set.
µ
Figure 20: Tx Interrupt Service Routine