Zilog Z86193 - Manual (Page 81)

Z8
®
CPU
User Manual
UM001604-0108 Input/Output Ports
74
Other Z8 MCUs feature a Port Configuration Register (PCON) for which Port 0 and Port 1
can be configured to provide open-drain outputs. The PCON Register is located in ERF
Bank F, Register
00h
. See Figure 62 on page 74.
Port 1 Open-Drain— Port 1, D1 can be configured as open-drain by resetting this bit (D1
= 0) or configured as push–pull active by setting this bit (D1 = 1). The default value is 1.
Port 0 Open Drain— Port 0, D2 can be configured as open-drain by resetting this bit (D2
= 0) or configured as push–pull active by setting this bit (D2 = 1). The default value is 1.
Low EMI Emission
Some Z8
®
MCUs can be programmed to operate in a Low EMI Emission Mode using the
Port configuration register (PCON). The PCON register allows the oscillator and all I/O
ports to be programmed in the Low-EMI Mode independently. Other Z8 MCUs may offer
a ROM Mask or OTP programming option to configure the Z8 MCU ports and oscillator
globally to a Low-EMI mode (where the XTAL frequency is set equal to the internal sys-
tem clock frequency.
Use of the Low EMI feature results in:
•
The output pre-drivers slew rate reduced to 10 ns (typical)
Figure 62. Port Configuration Register (Write-Only)
D7 D6 D5 D4 D3 D2 D1 D0
PCON (Fh) 00h
0 Port 1 Open Drain
1 Port 1 Push–pull Active *
0 P34, P37 Standard Output*
1 P34, P37 Comparator Output
Comparator Output Port 3
Low EMI Oscillator
0 Port 0 Open Drain
1 Port 0 Push–pull Active *
0 Port 0 Low EMI
1 Port 0 Standard *
0 Port 1 Low EMI
1 Port 1 Standard *
0 Port 2 Low EMI
1 Port 2 Standard *
0 Low EMI
1 Standard *
0 Port 3 Low EMI
1 Port 3 Standard *
* Default Setting After RESET