Zilog Z80230 - Manual (Page 276)

SCC/ESCC
User Manual
UM010903-0515 Application Notes
269
pin is driven from the same signal as CTS. To be compatible with this feature, connect J15-J4 to
pins 4 and 9 of the selected connector among J5-J10.
On the Mac SE, Mac II, and later models, a multiplexing scheme is provided on SCC channel A’s
RTxC pin to drive from either the same signal as DCD, or from an on-board 3.672 MHz clock.
Channel B always had the 3.672 MHz clock. The former capability can be provided by connecting
J15-J6 to pins 6 and 8 of the selected connector among J5-J10. The latter capability can be only
approximated using the 80186 clock with different baud rate divisors, or by using another oscilla-
tor. The board includes an unpopulated 4-pin oscillator socket that can be useful in this regard.
Jumper Summary
Table includes only those connector blocks intended to be populated by 2-pin option jumpers. J1-
J15 and J26 are actual connectors meant for use with cables, jumper wires, or wire wrapped 
connectors.
Two-Pin Option Jumpers
Jumpers Installed Open
J9-J7 thru -9 7 to 8: 80186 SYSCLK is IUSC RxC
7 to 9: 80186 SYSCLK is IUSC TxC
8: Something else on RxC, or N/C
9: Something else on TxC, or N/C
J10-J7 thru -9 7 to 8: 80186 SYSCLK is MUSC (USC A) RxC
7 to 9: 80186 SYSCLK is MUSC (USC A) TxC
8: Something else on RxC, or N/C
9: Something else on TxC, or N/C
J12-J7 thru -9 7 to 8: 80186 SYSCLK is USC B RxC
7 to 9: 80186 SYSCLK is USC B TxC
8: Something else on RxC, or N/C
9: Something else on TxC, or N/C
J16-J1 thru -3 1 to 2: J3, J4 TxD driven when RTS
2 to 3: J3, J4 TxD driven full-time
Must install one or the other
J17-J1 thru -2
J17-J3 thru -6
Unbalanced DCD- on J3 or J4
3 to 5 and 4 to 6: CTS+ on J4-J2
3 to 4 and 5 to 6: CTS- on J3 or J4
Differential DCD+,. DCD- on J3
Differential CTS+,. CTS- on J3
J18-J1 thru -3 1 to 2: 2764, 27128, 27256 EPROMs
2 to 3: 27512 EPROMs
Must install one or the other
J19-J1 thru -6 1 to 2 and 4 to 5: 128K x 8 SRAMs
2 to 3 and 5 to 6: 32K x 8 SRAMs
Must install one or the other
J20-J1 thru -3 1 to 2: U2 contains 80C30 or 80230
2 to 3: U2 contains 85C30 or 85230
Must install one or the other
J21-J1 thru -6 1 to 2 and 4 to 5: U2 contains 80C30 or 80230
2 to 3 and 5 to 6: U2 contains 85C30 or 85230
Must install one or the other
J22-J1 thru -4


1 to 2: MUSC (USC A) RxREQ on DMA 0
1 to 3: MUSC (USC A) RxREQ on DMA 1
2 to 4: MUSC (USC A) TxREQ on DMA 0
3 to 4: MUSC (USC A) TxREQ on DMA 1

1: MUSC (USC A) Rx no DMA
4: MUSC (USC A) Tx no DMA