Datasheet

DS_1215F_003 73S1215F Data Sheet

Rev. 1.4 23

Table 11: Port Registers

SFR

Address

R/W Description

USR70 0x90 R/W Register for User port bit 7:0 read and write operations (pins USR0…

USR7).

UDIR70 0x91 R/W Data direction register for User port bits 0:7. Setting a bit to 0 means that

the corresponding pin is an output.

USR8 0xA0 R/W Register for User port bit 8 read and write operations (pin *USR8).

UDIR8 0xA1 R/W Data direction register for port 1.

All ports on the chip are bi-directional. Each consists of a Latch (SFR USR70 to USR8), an output driver,

and an input buffer, therefore the MPU can output or read data through any of these ports if they are not

used for alternate purposes.

1.6 Instruction Set

All instructions of the generic 8051 microcontroller are supported. A complete list of the instruction set

and of the associated op-codes is contained in the 73S12xxF Software User’s Guide.

1.7 Peripheral Descriptions

1.7.1 Oscillator and Clock Generation

The 73S1215F has two oscillator circuits; one for the main CPU clock and another for the RTC. The

main oscillator circuit is designed to operate with various crystals or external clock frequencies. An

internal divider working in conjunction with a PLL and VCO needs to provide a 96MHz internal clock

within the 73S1215F. 96 MHz is the required frequency for proper operation of specific peripheral blocks

such as the USB, specific timers, ISO 7816 UART and interfaces and keypad. The clock generation and

control circuits are shown in Figure 3.