SHARP PC-G850V(S) User Manual -
Appendix A: 11-Pin Interface
6
SIO-Mode: Signal Levels
The next table summarizes the logic- and voltage-levels of the RS-232 standard in
comparison with UART-TTL and the PC-G850V(S).
Logic
level
Voltage level Semantics for data
signals (RXD,TXD)
Semantics for
control signals
(RTS,CTS,etc.)
RS-232
LOW
-15V to -3V
1 (Mark), Idle, Stop
Inactive
HIGH
+3V to +15V
0 (Space), Start
Active
UART-TTL
LOW
0V
0 (Space), Start
Active
HIGH
+3,3V / +5V
1 (Mark), Idle, Stop
Inactive
PC-G850V(S) LOW
0V
1 (Mark), Idle, Stop
Inactive
HIGH
5V
0 (Space), Start
Active
So the PC-G850V(S) exposes inverted UART-TTL level signals in SIO-mode, just as
most other SHARP pocket computers do. That means the logic is identical to the RS-232
standard (HIGH=0/active), but the voltage level is TTL.
ð
In order to connect peripheral devices with the PC-G850V(S) that operate at
RS-232 voltage levels, a level converter is mandatory!
The state of the TXD- and RTS-signals in SIO-mode is undefined, except for the
following cases:
1. The interface has explicitly been opened in SIO-mode (e.g.
OPEN“COM:“
) when in
operational main mode “BASIC”.
2. R- or W-commands are executed in operational main mode “Monitor”.
3. Data transfer via SIO in operational main mode “TEXT”.
