Thank for advice, Peter.
Then, in the last re-design I am just working with, I think that
I will still use the 4 wire 'bit-banging' as it was in the erlier one.

Or, parhaps, use the UART on the radio-unit ('slave-uP'), and
use a software-routines for rs232-com on master-card.
UART on master-card is alredy occupied by a gsm-modem..

However, for perifial communication I am using a SPI-UART
MAX3100, a very nice solution, but this circuit is very expensive,
so parhaps you have any suggests if there is any other SPI-UARTS.
I have search for alternative without any results.

Aboute Maxim-circuits, very good quality but generally very
expensive. I was also serching for alternative for reset-circuit, MAX810, which costs aboute $2.0 /1000pcs, and found LM810 instead and
orded 1000pcs for --$0.40. (exactly the same circuit).

PS/ sorry for my spelling in subject, and I did'nt say what cpu
I am using, AT89LS53.

chears - Magnus Munthe