Zilog Z80195 User Manual
Page 15
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EVELOPMENT
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UM951800100
Z
ILOG
ASCI0 DCE Pinning on J13
(Continued)
DTR on J13 is received onto J14-14 (/DSR0 on the schematic).
It can be jumpered to the 185’s
PIA12 pin on J14-13, or PIA11 on J14-15.
The signal on J14-16 (/DCD0O on the schematic) drives DCD on J13.
It can be jumpered from the
185’s PIA11 pin on J14-15, or PIA10 on J14-17.
The signal on J7-6 (CK0O on the schematic) drives both RxC and TxC (DCE source) on J13.
It
can be jumpered from the 185’s CKA0/CKS pin on J7-5, in which case the pin should be programmed
for the CKA0 function, and CKA0 should be programmed as a 1X clock output. In this case, ASCI0
will be able to receive data correctly only if the remote transmitter actually uses TxC (DCE source)
to clock data onto TxD.
TxC (DTE source) on J13 is received onto J7-4 (CK0I on the schematic).
It can be jumpered to
the 185’s CKA0/CKS pin on J7-5, in which case the pin should be programmed for the CKA0 function,
and CKA0 should be programmed as a 1X clock input.
No signal on J13 is received to the 185’s /DCD0/CKA1 pin, which is connected to J7-7.
A pull-
up resistor, on the DCD0 receivers used with J12, ensures that the signal at J7-8 will be asserted Low,
as required for ASCI0 reception if J7-7 is jumpered to J7-8 and software programs /DCD0/CKA1 for
the /DCD0 function.
ASCI1 and J9
Only one connector is provided for ASCI1, the DB-25 female J9. It includes only transmit and receive
data, no “modem control” or status signals. The jumper header J8 controls both the pinning of J9 (DTE
versus DCE) and the signaling type (RS-232 versus differential):
Function
Jumper Connections
RS-232 DCE pinning
J8-4 to J8-6, J8-7 to J8-8, and J8-9 to J8-10
RS-232 DTE pinning
J8-4 to J8-6, J8-7 to J8-9, and J8-8 to J8-10.
Differential DCE pinning
J8-1 to J8-2, J8-3 to J8-4, J8-7 to J8-8. and J8-9 to J8-10.
For differential DTE pinning
J8-1 to J8-3, J8-2 to J8-4, J8-7 to J8-9, and J8-8 to J8-10.
Differential receiving is compatible with RS-422 and RS-485. For ASCI1 and J9, differential
transmission differs from RS-422 and RS-485 in that it uses
±
5V swings. This is because it uses part
of the 26LS30 driver U17 that is used for LocalTalk/ AppleTalk on J16. However, this differential output
is compatible with most differential receivers as long as they can tolerate a voltage differential up to
10V without damage.