7188XA/B/C & 7521/2/2A/3/4/7 Series Hardware User’ s Manual, Ver. 3.0 Sep/2002, 7Mh-001-20 -----
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2.5 COM ports Comparison
The COM port of the 7188X/7521 series can be RS-232 or RS-485 as follows:
type
Pins name
2-wire RS-485
Data+, Data-
3-wire RS-232
Txd,Rxd,Gnd
5-wire RS-232
Txd,Rxd,Gnd,Rts,Cts
9-wire RS_232 Txd,Rxd,Gnd,Rts,Cts,Dcd,Dtr,Dsr,Ri
The COM ports of the 7188XA are given as follows:
COM port Hardware
COM1
16C550, 9-wire RS-232 or 2-wire RS-485
COM2
16C550, 2-wire RS-485
COM3
80188’ s on-chip UART-0, 3-wire RS-232
COM4
80188’ s on-chip UART-1, 3-wire RS-232
The programming of the 16C550 is very different from the 80188’s
UART. The interrupt handling of the 80188 is also very different from the
PC’ s 8259.
Therefore if the user downloads the PC’s RS-232 application
program into the 7188XA, it will not work.
The software driver of the 7188XA is an interrupt driven library that
provides a 1K QUEUE buffer for every COM port. The software is well
designed & easy to use.
The software driver provides the same interface for all 4 COM ports. The
user can use these COM port in the same way without any difficulty.
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