Z84C90_12 Datasheet, PDF (34/56 Pages) Zilog, Inc. – KIO Serial/Parallel Counter/Timer

Z84C90 KIO Serial/Parallel Counter/Timer
Product Specification
27
I/O7 I/O6 I/O5 I/O4 I/O3 I/O2 I/O1 I/O0
0 = Sets bit to output
1 = Sets bit to input
Figure 30. PIA Control Register
KIO Command Register
Command Register A is used to program software resets and to configure the internal
interrupt daisy chain priority (see Figure 31). This register should be programmed before
all others. The reset control bits are momentary; writing a 1 pulses an internal reset signal
to the appropriate device.
D7 D6 D5 D4 D3 D2 D1 D0
Daisy Chain Configuration
000 None
001 SIO, CTC, PIO
010 SIO, PIO, CTC
011 CTC, SIO, PIO
100 CTC, PIO, SIO
101 PIO, SIO, CTC
110 PIO, SIO, CTC
111 None
Daisy chain write enable
Reset PIO
Reset CTC
Reset SIO
SIO/PIA mux
0 = PIA
1 = SIO
Figure 31. KIO Command Register A
Z84C90 KIO: Enhanced Version
A subsequent revision of the Z84C90 MCU features an enhancement which allows users
to simulate the Return From Interrupt sequence with software. This feature allows the
interfacing of the CPU to other devices in addition to the Z80 CPU (or the Z180/Z280).
PS011804-0612
Z84C90 KIO: Enhanced Version