C511_1 Datasheet, PDF (105/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

EEPROM Programming Interface
SAB-C513A-H
9.2.1 Selection of the Programming Mode
The programming mode is selected by applying specific logic levels to the four PMS0-3 pins of the
SAB-C513A-H.
Table 9-2
Programming Mode Selection Pins
Mode
Normal Mode
Programming Mode
PMS3
(RESET)
1 or 0
1
PMS2
(PSEN)
none
0
PMS1
(ALE)
none
1
PMS0
(EA)
0 or 1
0
Note that PMS3 has to be active (’1’) during the whole programming mode operation. During normal
operation PMS2 and PMS1 are outputs (PSEN, ALE) and no external driving circuitry should be
connected to these pins.
It should be also noted, that always a clock has to be supplied in programming mode and that the
operating voltage is restricted to 5 V ± 10%.
9.2.2 Resetting the Programming Interface
By applying a high level to the PRES pin the contents of the programming interface registers will be
set to their initial values. When entering the programming mode, PRES should be held high.
The programming interface must not be reset while programming or erasing the EEPROM (PROG
bit =1). The program or erase cycle should be finished properly before resetting the interface.
9.2.3 Interface Bus Operation
The programming interface with its registers can be accessed via a Intel type multiplexed bus
interface. Figures 9-9-4 and 9-9-5 illustrate a read and a write access to the registers. To enable
access to the programming interface the enable input PCS must be active during the entire access
cycle (from leading edge of ALE until trailing edge of RD or WR). PCS should always be deactivated
between subsequent accesses to the programming interface. With the falling edge of ALE the
address of the register to be accessed is latched. The read signal puts the contents of the selected
register onto the bus. During write cycles the write signal latches the data bus content into the
selected register. Each read and write cycle must be initiated by a PALE high pulse.
Semiconductor Group
9-5