604 Part 3 ½Computer Classes Section 1½ Monolithic Microcomputers
Descriptions of these various elements appear in the following sections.
II. Mp State
The Program ROM contains 6144 bits organized as 512 twelve-bit words. RAM storage consists of 32 eight-bit registers, all of which are addressable by instructions contained in the program ROM. These registers are divided into two functional groups: operation al registers and general-purpose registers. The general registers are addressed as F9 to F31 and contain data and control information. These registers are all located in a contiguous block labeled "Register File Array" in Fig. 1. The operational registers, F0 to F8, are scattered throughout the chip, and not only are they addressable by the program, but they also perform special functions described in Sec. III of this chapter.
III. Pc State
The register file arrangement is delineated as follows:
b F1<7:0>\Real.Time. Clock. Counter. Register. This register counts external events by incrementing on the falling edge of the RTCC pin. This register can also be loaded and read under program control.
c F2<8:0>\Program.Counter (PC). The program counter points
to the next instruction to be executed in memory. This register is 9 bits
wide to address the 512-word ROM, but only the low-order 8 bits can be
written to or read from