Motorola 68HC08LD - Manual (Page 7)

 iSYSTEM, March 2004 7/12
Voltage settings
J1 (on the top board)
Jumper selector J1 on the top board determines the operational voltage.
Position Vcc level
Set (*) 5.0 V
Removed 3.3 V
Jumper J1 settings (* - factory default)
This jumper must be set in any way regardless if the power supply is set to Emulator or to Target.
Ports
Original ports A and B are used for emulation and rebuilt by a port replacement unit. Therefore, electrical
characteristics are changed. Because of different technology used in the original chip and the port replacement
unit, the POD is not 100% electrically identical to the CPU. These (electrical) differences usually do not matter,
until it is relied upon its limits (i.e. max. VIL, min. VIH, max. input current, input resistance, etc.).
Ports A and B also feature alternate functions, i.e. ADC and Keyboard interrupts. The ADC convertor is original,
just the ADC selection is done using analog switches.
The Keyboard interrupt logic is emulated on the POD. The POD recognizes the KBSCR and KBIER register
configuration and emulates it and generates interrupts to the CPU.
A Port Replacement Unit (PRU) is used to emulate the rebuilt ports. The rebuilt port A has pull-up registers
constructed on the POD for the ports that can also be used as keyboard interrupts. The pull-up resistor value is
defined by the resistor network, inserted into the GR2 socket. The default value for the resistor network is 22k.
The pull-ups must always be defined by setting the jumpers. Jumpers J4 through J11 set the Port A pull-ups
(J4..J11 for PTA0..PTA7).
Whenever operating close to electrical limits and having problems with rebuilt ports, please check pull-up and
pull-down resistors on the problematical port. They should be neither too strong nor too weak. Check the voltage
level. Try to withdraw from voltage limits.
The jumpers P1_0 through P1_7 configure PORT A pull-up resistors GR2 (22k by default).
Configuration:
Jumper Set Removed
J4 Pull-up enabled on PTA0 No Pull-up
J5 Pull-up enabled on PTA1 No Pull-up
J6 Pull-up enabled on PTA2 No Pull-up
J7 Pull-up enabled on PTA3 No Pull-up
J8 Pull-up enabled on PTA4 No Pull-up
J9 Pull-up enabled on PTA5 No Pull-up
J10 Pull-up enabled on PTA6 No Pull-up
J11 Pull-up enabled on PTA7 No Pull-up
Jumper P1_0 through P1_7 settings (* - factory default)