MSK Modem
14
MX809
6.4 TX Timing
A – Address bytes
C – Checksum bytes
D – Data bytes
H – Hang bit
P – Preamble bytes
- Don’t care state
TX only – In TX, Preamble, and SYNC are
loaded as data from the microcontroller.
6.4.1 TX More Than One Message, SYNC Before Every Message, TX Checksum Enabled
RX/TX
TX OUTPUT
P1 P2
P
S1
S2 A1 A2
A3 A4 A5
A6 C1 C2
S1
S2
D1 D2 D3 D4 D5 D6
NOTE 6
IRQ
READ STATUS
REGISTER
TX DATA READY
WRITE TO
TX DATA BUFFER
P1 P2
P
S1 S2
A1 A2
A3 A4 A5 A6
S2
S1
D1 D2
D3 D4 D5 D6
CHECKSUM
ON/OFF
Figure 5: TX More Than One Message, SYNC Before Every Message, TX Checksum Enabled
Notes:
1. Preamble and SYNC bytes are loaded as data from the microcontroller.
2. The TX output will be held at bias level when no data is being transmitted.
3. TX byte synchronization is established by loading of the first preamble byte from the microcontroller.
4. Checksum must be turned off during preamble and SYNC words.
5. When RX / TX is low, TX output is at bias.
6. Any number of preamble bytes can occur here.
6.4.2 TX More Than One Message, TX Checksum Not Enabled.
RX/TX
TX OUTPUT
P1 P2
P
S1 S2 A1 A2
A3 A4
A
S1
S2 D1 D2 D3 D4
D
S1 S2 D1
NOTE 2
NOTE 3
NOTE 3
IRQ
READ STATUS
REGISTER
TX DATA READY
WRITE TO
TX DATA BUFFER
P1
P2
P
S1 S2 A1 A2
A3 A4
A
S1 S2
D1 D2
D3 D4
D
S1 S2 D1 D2
CHECKSUM
ON/OFF
Figure 6: TX More Than One Message, TX Checksum Not Enabled.
Notes:
1. Preamble, SYNC words and checksums are supplied by the microcontroller in this format as data bytes.
2. Any number of preamble bytes can occur here.
3. Any number of address/data bytes can occur here.
ꢀ1998 MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480036.004
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All trademarks and service marks are held by their respective companies.
CMLMICRO [ CML MICROCIRCUITS ]
