EM78M611E
Universal Serial Bus Series Microcontroller
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Product Specification (V1.1) 11.22.2006
(This specification is subject to change without further notice)
The following subsections describe each of the Operation Registers of the Sp ecial
Purpose Registers. The Operation Registers are arranged according to the order of the
registers’ addr ess. Note that some registers are read only, while ot hers are both
readable and writable.
8.2.2.1 R0 (Indirect Addressing Register) Default Value: (0B_0000_0000)
R0 is n ot a physically implemented register. Its major function is as an indirect
addressing pointer. Any instruction using R0 as a pointer actually accesses data
pointed by the RAM Select Register (R4).
8.2.2.2 R1 (Timer / Clock Co unter) Default Value: (0B_0000_0000)
The TCC register is an 8-bit tim er or counter. It is readable and writable as any other
register. The Timer m odule will be incremented after execution of every instruction
cycles. User can work around this by writing an adjusted value. The Timer interrupt is
generated when the R1 register overflows from FFh to 00h. This overflow sets bit TCIF
(RF[0]). The interrupt can be m asked by clearing bit TCIE (IOCF[0]). After Pow er-on
reset and Watchdog reset, the initial value of this register is 0x00.
8.2.2.3 R2 (Program Counter & Stack) Default Value: (0B_0000_0000)
The EM78M611E Program Counter is a 13-bit register that allows accessing of the 6k
words of the Program Mem ory with 8 level stacks. The eight LSB bits, A0~A7, are
located at R2, while the three MSB bits, A12~A10, are located at R3. The Program
Counter is cleared after Power-on reset or Watchdog reset. The first instruction that is
executed after a reset is located at address 00h.