Z8 Microcontrollers
I/O Ports ZiLOG
5-28 UM001601-0803
5.9 OPEN-DRAIN CONFIGURATION
All Z8s can configure Port 2 to provide open-drain outputs by
programming the Port 3 Mode Register (P3M) bit D0=0.
Other Z8s that have a Port Configuration Register (PCON) that
can configure Port 0 and Port 1 to provide open-drain outputs.
The PCON Register is located in Expanded Register File (ERF)
Bank F, Register 00H. See Figure 5-35.
Port 1 Open-Drain (D1). Port 1 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 (D2). Port 0 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.
5.10 LOW EMI EMISSION
Some Z8s can be programmed to operate in a Low EMI Emis-
sion Mode using the Port configuration register (PCON). The
PCON register allows the oscillator and all I/O ports to be pro
-
grammed in the Low-EMI Mode independently. Other Z8s may
offer a ROM Mask or OTP programming option to configure the
Z8 Ports and oscillator globally to a Low-EMI mode (where the
XTAL frequency is set equal to the internal system clock fre
-
quency.
Use of the Low EMI feature results in:
• The output pre-drivers slew rate reduced to 10 ns (typical).
• Low EMI output drivers have resistance of 200 Ohms
(typical).
• Low EMI Oscillator.
• All output drivers are approximately 25 percent of the
standard drive.
• Internal SCLK/TCLK = XTAL operation limited to a
maximum of 4 MHz - 250 ns cycle time, when Low EMI
Oscillator is selected and system clock (SCLK=XTAL, SMR
Reg. Bit D1=1).
Figure 5-34. Port 2 Configuration
Figure 5-35. Port Configuration Register (PCON) (Write-
Only)
D7 D6 D5 D4 D3 D2 D1 D0
(Write-Only)
0= Pull-Ups Active
Port 2 Configuration
1= Pull-Ups Open-Drain
Port 3 Mode Register
Register F7H
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
To Next Page
Loading...
Need help?
General
