INTERNAL SPECIFICATIONS

4.4 Special Function Registers (TCON, SCON,.... ACC, B)

4.4.1 Outline

As can be seen from the configuration shown in Table 4-6, the MSM80C154S/ MSM83C154S special function registers consist of 27 8-bit registers.

Special function registers can be accessed (R/W) by either data addressing or bit addressing. All 27 registers can be specified by data addressing. 13 registers (P0, P1, P2, P3, TCON, T2CON, SCON, IE, IP, PSW, ACC, B, and IOCON) can be specified by bit addressing.

If a register which does not exist at the data address is accessed when a special function register is used, the read data becomes 0FFH. And when data is written, none of the registers in the CPU are effected at all. Note, however, that since a jump is always executed when a bit test instruction which results in a relative jump at data condition “1” is executed, make sure that no instruction is executed for a register which does not exist.

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Sonic Alert msm83c154s, msm80154s, msm85c154hvs user manual Special Function Registers TCON, SCON,.... ACC, B, Outline