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HP 27130B
1/0
Address Space
The Z-80B CPU provides addressing capability for 256 distinct I/O port registers. The l\1UX
card uses only 47 I/O port register addresses: 16 are reserved for the four Z- 80 SIOs, 12 are reserved
for the three Z-80 CTCs, 12 are reserved for the MIC, and seven are reserved for the BIC.
Table 3- 3 shows the I/O addresses used by the card.
I
CAUTION
I
THE USE OF ANY OTHER ADDRESSES MAY CAUSE
IMPROPER OPERATION.
Z -80B Microprocessor CPU
The
z-
SOB CPU (U33) is an MOS LSI microprocessor which operates from a single + 5-volt supply,
uses a single-phase clock, and has a typical instruction execution time of 1 microsecond. The data
bus is eight bits wide, and the address bus is 16 bits wide. All CPU pins are TTL compatible.
The Z-SOB CPU uses a register-based architecture which includes two sets of six general-purpose
registers which can be used as individual S-bit registers or 16-bit register pairs.
Additional 8-bit
registers include two sets of accumulator and flag registers, and the interrupt vector and mernory
refresh registers. Additional 16-bit registers include the stack pointer, program counter, and two
index registers.
The Z- 80B CPU provides the intelligence for the MUX card to function as a
preprocessor for the I/O devices, thus relieving the host
computer of
a considerable amount of
processIng.
The functions of the Z-80B CPU signals are shown in table 3-4.
Z -80
S10/2
(Serial
1/0
Controller)
The MUX card uses four Z-80 S10/2 controller circuits (U43, U53, U63, and U73, see A42,
7-1). The Z-80 SIO/2 is a programmable serial I/O controller with two independent full-duplex
channels, each of which contains separate control and status lines. Each channel can be indepen-
dently programmed. On the MUX card, each of the eight channels is used as a fully programmable
asynchronous terminal controller.
Each SIO channel has two I/O addressable ports: one port for data transfer, and one for control in-
formation. Each control port has three read registers and eight write registers available for con-
trol information. The functions performed by the registers are shown in table 3-5.
Several of the SIO number 0 (U43) and SIO number 1 (U53).modem control output and modem
status input signals are used. for special functions, such as turning on the card's'LED, "sensing the
diagnostic:testhood,etc. These special functions are described in table 3-6.
3-7
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