Jameco Electronics 3000 User Manual

The slave port lines are shown in Figure 13-1. The function of these lines is described 
below.

SD0–SD7—These are bidirectional data lines, and are generally connected to the data 
bus of the master processor. Multiple slaves can be connected to the data bus. The slave 
drives the data lines only when /SCS and /SRD are both pulled low.

SA1, SA0—These are address lines used to select one of the four data registers of the 
slave interface. Normally these lines are connected to the low-order address lines of the 
master. The master always drives these lines which are always inputs to the slave.

/SCS—Input. Slave chip select. The slave ignores read or write requests unless the chip 
select is low. If a Rabbit is used as a master, this line can be connected to one of the 
master’s programmable chip select lines /I0–/I7.

/SRD—Input. If /SCS is also low, this line pulled low causes the contents of the register 
selected by the address lines to be driven on the data bus. If a Rabbit is used as a master, 
this line is normally connected to the global I/O read strobe /IORD.

/SWR—Input. If /SCS is also low, this line causes the data bits on the data bus to be 
clocked into the register selected by the address lines on the rising edge of /SWR or 
/SCS, whichever rises first. If a Rabbit is used as a master, this line is normally con-
nected to the global I/O write strobe /IOWR.

/IORD
/IOWR

A0
A1

/SRD
/SWR
SA0
SA1

/SLAVEATTN

INT0A

/RESET

/SCS

/I7

/XTALB1

CLK

/I6

/SCS

/SLAVEATTN

INT1A

portout

SMODE0

SMODE1

+

SMODE0

SMODE1

+

Reset
Pulldown