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SAF-C509-L Datasheet(PDF) 8 Page - Siemens Semiconductor Group |
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SAF-C509-L Datasheet(HTML) 8 Page - Siemens Semiconductor Group |
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8 / 74 page  Semiconductor Group 7 09.96 C509-L P2.0 – P2.7 14-21 I/O Port 2 is a 8-bit I/O port. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application it uses strong internal pullup resistors when issuing 1s. During accesses to external data memory that use 8-bit addresses (MOVX @Ri), port 2 issues the contents of the P2 special function register. P2.0 - P2.7 A8 - A15 Address lines 8 - 15 PSEN / RDF 22 O Program Store Enable / Read FLASH The PSEN output is a control signal that enables the external program memory to the bus during external code fetch operations. It is activated every third oscillator period. PSEN is not activated during external data memory accesses caused by MOVX instructions. PSEN is not activated when instructions are executed from the internal Boot ROM or from the XRAM. In external programming mode RDF becomes active when executing external data memory read (MOVX) instructions. ALE 23 O Address Latch Enable This output is used for latching the low byte of the address into external memory during normal operation. It is activated every third oscillator period except during an external data memory access caused by MOVX instructions. EA 24 I External Access Enable The status of this pin is latched at the end of a reset. When held at low level, the C509-L fetches all instructions from the external program memory. For the C509-L this pin must be tied low. PRGEN 25 I External Flash-EPROM Program Enable A low level at this pin disables the programming of an external Flash-EPROM. To enable the programming of an external Flash-EPROM, the pin PRGEN must be held at high level and bit PRGEN1 in SFR SYSCON1 has to be set. There is no internal pullup resistor connected to this pin. *) I = Input O = Output Table 1 Pin Definitions and Functions (cont’d) Symbol Pin Number I/O*) Function |
Similar Part No. - SAF-C509-L |
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Similar Description - SAF-C509-L |
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