GMSK Modem Data Pump
Page 13 of 37
MX909A PRELIMINARY INFORMATION
In this way the µC can read data and write a new task to the modem while the received bits needed for this
new task are being stored in the De-interleave Buffer. See Figure 8.
The above is not true for loading the Frame Sync detection bytes (LFSB): the bytes to be compared with the
incoming data must be loaded prior to the task bits being written.
Detailed timings for the various tasks are given in Figure 9 and Figure 10.
Data from µC to Data Buffer
Task 1 data
Task 2 data
Task and/or Commands from µC
to Command Register
Status Register BFREE Bit
Status Register IRQ Bit
IRQ Output (IRQEN = '1')
TXOUT Signal
from Task 1
from Task 2
Figure 7: Transmit Process
RXIN Signal
for Task 1
for Task 2
IRQ Output (IRQEN = '1')
Status Register IRQ Bit
Status Register BFREE Bit
Task from µC
to Command Register
Task 1
Task 2
Task 1 data
Data from Data Buffer to µC
Figure 8: Receive Process
Mobitex¥ Modem Tasks
B2 B1 B0
Receive Mode
Transmit Mode
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
NULL
SFH
R3H
RDB
SFS
NULL
T7H
Search for Frame Head
Read 3 byte Frame Head
Read Data Block
Transmit 7 byte Frame Head
Reserved
TDB
TQB
TSB
TSO
Transmit Data Block
Transmit 4 Bytes
Search for Frame Sync
Read Single Byte
RSB
LFSB
Transmit Single Byte
Transmit Scrambler Output
Load Frame Sync Bytes
RESET Cancel any current action
RESET Cancel any current action
4.4.2.5 NULL - No effect
This task is provided so that a AQBC or AQLEV command can be initiated without loading a new task.
¤2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480134.005
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